Accepted Manuscript Towards the development of clinical measures for spinal cord injury based on the International Classification of Functioning, Disability and Health with Rasch analyses Carolina S. Ballert , Msc Dpl Stat Gerold Stucki , Prof Fin Biering-Sørensen , Prof Alarcos Cieza , Prof PII:
S0003-9993(14)00398-0
DOI:
10.1016/j.apmr.2014.05.006
Reference:
YAPMR 55842
To appear in:
ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION
Received Date: 23 January 2014 Revised Date:
6 May 2014
Accepted Date: 9 May 2014
Please cite this article as: Ballert CS, Stucki G, Biering-Sørensen F, Cieza A, Towards the development of clinical measures for spinal cord injury based on the International Classification of Functioning, Disability and Health with Rasch analyses, ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION (2014), doi: 10.1016/j.apmr.2014.05.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Full title: Towards the development of clinical measures for spinal cord injury based on the International Classification of Functioning, Disability and Health with Rasch analyses
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Running head: Psychometric properties of ICF categories for functioning in SCI
Authors: Msc Dpl Stat Carolina S. Ballert1,2,3, Prof Gerold Stucki1,2,3, Prof Fin Biering-
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Sørensen4, Prof Alarcos Cieza1,5,6
Swiss Paraplegic Research (SPF), Nottwil, Switzerland
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Department of Health Sciences and Health Policy, University of Lucerne
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ICF Research Branch of WHO Collaborating Center for the Family of International Classifications in
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German
Clinic for Spinal Cord Injuries, Glostrup Hospital and Faculty of Health and Medical Sciences,
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University of Copenhagen, Copenhagen, Denmark Faculty of Social and Human Sciences, School of Psychology, University of Southampton, UK
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Department of Medical Informatics, Biometry and Epidemiology – IBE, Chair for Public Health and
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Health Services Research, Research Unit for Biopsychosocial Health, Ludwig-Maximilians-University (LMU), Munich, Germany
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Acknowledgements: The author wants to thank Ursula Ludgate, Alan Tennant, and
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Bernd Fellinghauer for their valuable input, feed-backs and support.
Conflict of interest:
Corresponding author & Request for Reprints :
Faculty of Social and Human Sciences School of Psychology
Highfield Campus Southampton SO17 1BJ
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University of Southampton
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Telephone: +44 23 8059 7549 Facsimile: +44 23 8059 4597
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Professor Alarcos Cieza
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The authors declare no conflict of interest.
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Full title: Towards the development of clinical measures for spinal cord injury
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based on the International Classification of Functioning, Disability and Health
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with Rasch analyses
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Running head: Psychometric properties of ICF categories for functioning in SCI
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Abstract:
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Objectives: To determine whether ICF categories relevant to SCI can be
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integrated in clinical measures and get insights to guide their future
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operationalization. Specific aims are to find out whether the ICF categories
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relevant to SCI [1] fit a Rasch model taking into consideration the dimensionality
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found in previous investigations, [2] show local item dependencies (LID), or [3]
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differential item functioning (DIF).
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Design: All second level ICF categories collected in ‘Development of ICF Core
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Sets for SCI’ project in specialized centers within fourteen countries from 2006-
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2008.
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Setting: Secondary data analysis
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Participants: 1048 adults with SCI from the early post-acute and the long-term
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living context.
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Interventions: n.a.
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Main Outcome Measures: Two unidimensional Rasch analyses one for the
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ICF categories from body functions and body structures components and
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another for the ICF categories from the activities and participation component.
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Results: [1] Results support good reliability and targeting of the ICF categories in both dimensions. In each dimension few ICF categories were subject to
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misfit. [2] Local item dependency was observed between ICF categories of
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same chapters, [3] and group effects for age and gender only to a small extent.
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Conclusion: The validity of ICF categories to develop measures of functioning
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in SCI for clinical practice and research is to some extent supported. Model
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adjustments were suggested to further improve their operationalization and
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psychometrics.
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Keywords: ICF, Paraplegia, Tetraplegia, Spinal Cord Injuries, IRT, Rasch
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Abbreviations: ICF (International Classification of Functioning, Disability and
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Health), WHO (World Health Organization), SCI (spinal cord injury), LID (local
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item dependence), DIF (differential item functioning), BF (body functions), BS
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(body structures), A&P (activities and participation), EF (environmental factors),
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PSI (persons separation index), KR-20 (Kuder-Richardson formula 20), SD
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(standard deviation), SE (standard error).
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INTRODUCTION
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The International Classification of Functioning, Disability and Health (ICF)
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provides a unified language and framework to describe human functioning and
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its external, environmental influences 1. The ICF has been introduced by the
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World Health Organisation (WHO) to improve the data collection and their
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comparability across patients, institutions, settings and countries.
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The ICF is organized in a hierarchical structure starting from the most general
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component level including body functions, coded with the letter b-, body
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structures, coded s-, activities and participation, coded d-, and environmental
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factors, coded e-. In the components, the chapters are included and coded with
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a number in addition to the letter of the component (e.g. b2 Sensory functions
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and pain). The chapters are further specified with second, third and fourth level
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categories which are coded by adding two, three or four digits to the chapter
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(e.g. b280 Sensation of pain, b2801 Pain in body part, and b28014 Pain in
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upper limb). With a rating scale called “qualifier scale” the level of impairment or
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difficulty in each ICF category can be indicated on a five level rating scale from
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0 to 4. With both, the categories and qualifiers, the ICF has been used for the
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description and the assessment of functioning.
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However, the development of valid clinical measures needs to include a number
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of steps which range from the selection of domains, the testing of their
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dimensionality and their psychometric properties to their operationalization with
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items or clinical tests, and final testing of their psychometric properties. In the
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field of spinal cord injury (SCI) different steps have already been carried out.
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First, Brief and Comprehensive ICF Core Sets for individuals with SCI in the
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early post-acute and the long-term phase have been developed. This took place
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in a consensus conference using evidence from preliminary studies. When
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implementing them in clinical practice, the Brief ICF Core Sets are the starting
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points. The Comprehensive ICF Core Sets represent the pool from which
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additional ICF categories can be selected if relevant for the patient. This
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approach facilitates the implementation of the ICF in clinical practice 2. In a
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follow-up study, we identified ICF categories from the Comprehensive Core
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Sets for SCI 3, 4 that best differentiate among different levels of self-reported
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health 5 and tested the robustness of the dimensionality of those ICF categories
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together with those of the Brief ICF Core Sets.
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In this study we will concentrate on the psychometric properties of the ICF
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categories, since this can also provide insights for their operationalization. We
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build, thereby, on knowledge gathered from previous studies with ICF Core Sets
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in which clinical measures of functioning were developed6-15. The psychometric
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analysis will allow to determine whether the ICF categories relevant for SCI can
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be used as a clinical measure and also guide the selection of items, in case of
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the development of a patient reported questionnaire. For example, if an ICF
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category has two different levels of difficulty in subgroups (e.g. males and
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females), group specific items are probably needed for further operationalization
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of that ICF category.
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The overall objectives of this investigation are to determine whether the ICF
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categories relevant to SCI can be integrated in clinical measures and get
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insights to guide the future operationalization with items of those ICF
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categories.
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The specific aims are to find out whether [1] the ICF categories relevant to SCI
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fit the Rasch model taking into consideration the dimensionality found in
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previous investigations, i.e. body functions (BF) and body structures (BS) as
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one dimension and activities and participation (A&P) as a second dimension, [2]
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the ICF categories show local item dependencies (LID), or [3] differential item
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functioning (DIF).
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Study Design
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Explorative psychometric study using data collected in a cross-sectional, multi-
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center study carried out in the international project ‘Development of ICF Core
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Sets for Spinal Cord Injury’ in sixteen SCI specialized centers within fourteen
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countries from 2006-2008. Persons with traumatic SCI, > 18 years, who
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understood the purpose of the study and signed informed consent, were
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included. Only persons with traumatic brain injury or having been diagnosed
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with a mental disorder prior to the SCI were excluded. The clinical and
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sociodemographic information collected and exclusively used to describe the
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study population are shown in Table 1. Participants did not receive any
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incentive to participate.
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Data collection was approved by the ethics committees in charge of the study
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centers involved and performed in accordance with the Declaration of Helsinki.
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Study Population
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A total of 1048 persons with SCI participated in this study; 489 from the early
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post-acute and 559 from the long-term context (Table 1). Four hundred and
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twenty five participants were citizens of middle/low resource countries
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(Malaysia, South Africa, Brazil, Thailand, India and Vietnam) and 623 from high
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resource countries (USA, Switzerland, Denmark, Canada, Australia, Germany,
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New Zealand and Israel).
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Data Collection
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After having collected the clinical and demographic information, professionals
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collected data using a checklist containing all second-level categories of the ICF
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(N = 264). The impairment/difficulty in the ICF categories was recorded
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dichotomously; with 1 indicating an impairment/difficulty. Additional information
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about data collection procedures can be found elsewhere16.
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The focus of this study is on ICF categories describing functioning in SCI, i.e.
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ICF categories of BF&BS and A&P. We included in the analyses the ICF
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categories from the Brief Core Set for SCI for the early post-acute and long-
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term context and statistically selected ICF categories that best capture levels of
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patients’ and health professionals’ reported general health of persons with SCI
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in the early post-acute and long-term living context 5. ICF categories that were a
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problem for more than 90% of the participants were also included. This made
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up in total 64 ICF categories (29 BF, 4 BS and 31 A&P). It is important to
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emphasize that ratings of the ICF categories and not items developed to
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measure them are used in these analyses.
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All included ICF categories are shown in the first two columns of Table 2 and 3.
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The ICF categories of the Brief ICF Core Sets selected by experts are marked
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with ‘c’, those coming from the statistical selection with ‘°’ and those which
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represent a problem for more than 90% of the participants with ‘+’.
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Statistical Analysis
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Unidimensional Rasch analyses 17 were used to determine the models fit and
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the psychometric properties of the ICF categories selected for this study. We
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opted for unidimensional Rasch because the presence of these two dimensions
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had already been identified in a previous study based on multi-dimensional
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Rasch18. The dimensions that we intended to capture are “impairment in body
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functions” and “difficulties in activities and participation domains”.
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The Rasch model provides an item and a person estimate. The estimate of the
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person is called the persons’ ability and tells about the ranking of each person
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on the dimensions’ continuum. The estimate of the item is called the item
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difficulty and informs about the position of the item in the same continuum.
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The models’ reliabilities were assessed using the KR-20 index and the person
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separation index (PSI). They inform about the internal consistency of the Rasch
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estimates 19 and are interpreted in the same way as a Cronbach’s alpha 20.
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A good targeting is achieved when the spectrum of difficulties of the ICF
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categories match the abilities of the persons. Furthermore, a scale is free of
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ceiling and floor effects when less than 15% of the persons’ abilities exceed the
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most difficult ICF category and less than 15% of the persons’ abilities are below
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the easiest ICF category 21. The quality of the coverage of the ICF categories on
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the measurement continuum will be illustrated with the person-item map, which
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displays a visual ruler of the estimated ICF category difficulties and the
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frequency of persons with the associated level of ability. Persons’ ability
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histograms are expected to be bell-shaped.
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A good item fit is achieved when the observed data are close to the expected
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data. The items’ fit is provided by the outfit and infit mean squared errors22. An
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item`s goodness and its usability for measurement is confirmed when the mean
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squared infit and outfit are between 0.5 and 1.5
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the pattern of responses. Outfit is more sensitive to responses to items with
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difficulty far from a person.
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Local Item Dependency (LID) assumption was verified with a correlational
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analysis of the standardized residuals of the Rasch analysis 25. High
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correlations (|r|>0.3) indicate LID between two ICF categories.
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The Differential Item Functioning (DIF) testing included groups of age (below
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and above the median age 41.2 years) and gender, and used the Wald test to
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compare Rasch parameters of each ICF category by group 26.
. Infit is more sensitive to
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All Rasch analyses were performed with the R-package eRm 27. Instead of
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setting the average item difficulties to zero, we restricted the first item to be
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zero, which is the default setting in this package. Benjamini-Hochberg
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correction for multiple testing, controlling the false detection rate, was applied
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for the p-values of the ICF categories’ DIF analysis 28 because the same
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person’s ratings were submitted twice to the DIF analysis for each of the 2
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different sub-groups (age and gender).
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Results
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The sociodemographic and clinical characteristics of the participants are
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presented in Table 1. High resource countries show a higher prevalence of
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persons with tetraplegia (50.9% vs. 37.2%), more persons living alone (25.8%
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vs. 5.7%), less transportation accidents (51.8% vs. 34.3%), and more non-
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traumatic spinal cord dysfunctions (38% vs. 18%).
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A total of 33 ICF categories were included in the analyses of the dimension
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BF&BS and 31 in the dimension of A&P. The first Rasch analysis for each
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dimension detected misfitting persons (person infit statistic |θ|>2.5), which were
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excluded. The following analyses were carried out with 1036 participants in the
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BF&BS dimension and 1020 participants in the A&P dimension.
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Model fit
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The estimates for the internal consistency indicate a good to excellent reliability
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of the Rasch models (BF&BS: KR-20=0.85 and PSI=0.86; A&P: KR-20=0.90
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and PSI=0.89).
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The ICF categories’ difficulties are well-targeted on the persons’ abilities. In the
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BF&BS dimension the mean ICF category difficulty was -0.06 (SD=1.79) and
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the mean person ability 0.10 (SD=1.29). For the A&P dimension the mean ICF
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category difficulty was -0.09 (SD=1.65) and the mean person ability 0.29
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(SD=1.56). The person-item maps on Figure 1 and 2 show that the continuum
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of the scale is well addressed for the BF&BS dimension, but the A&P dimension
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presents a gap of more than 1.5 logit from d450 Walking to d420 Transferring
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oneself. In both dimensions, the increases in difficulty on the continuum
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included 18% of logit changes ≤0.05 for the BF&BS and 35% for the A&P ICF
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categories. This indicates that the measurement continuum could be addressed
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with fewer ICF categories than available. Ceiling or floor effects were not
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observed.
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Fit of the ICF categories
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Table 2 and 3 present the results of the psychometric investigation of the ICF
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categories with their difficulties, the standard error (SE), and the difficulty rank
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for the BF&BS and A&P dimensions respectively. In addition, Table 2 reports
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the infit and outfit MSQ statistics.
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All categories of BF&BS present infit statistics between 0.5 and 1.5 and only
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one shows outfit statistics above 1.5, namely s810 structure of areas of skin.
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Also, in the A&P dimension, all infit statistics lie between 0.5 and 1.5. Three
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A&P categories, however, show outfit statistics above 1.5, namely d240
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Handling stress and other psychological demands, d820 School education, and
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d930 Religion and spirituality.
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ICF categories with outfit statistics above 1.5 indicate categories which under-
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discriminate, i.e. they do not differentiate well different levels of the continuum.
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The columns entitled LID of Table 2 and 3 indicate the locally dependent ICF
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categories. Further, the 17 ICF categories of BF&BS showing LID are depicted
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graphically in Figure 3 while those 15 from A&P in Figure 4. In general, ICF
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categories show local dependencies with others from the same chapter and
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with those with which they are related from a functional point of view, e.g. b810
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Protective functions of the skin and s810 Structure of areas of skin.
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The ICF categories with DIF for age and gender are presented in Table 2 and 3.
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In the A&P dimension, no DIF is found for gender and for five ICF categories in
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the age group (16.13%). In the BF&BS dimension, age and gender groups
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counted respectively 4 (12.12%) ICF categories with DIF.
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Discussion
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The results of this investigation show the validity of the ICF categories relevant
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for SCI to capture the whole spectrum of functioning from low to high levels in
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two dimensions.
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In both dimensions there is an intuitive and meaningful progression in the order
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of ICF categories. In BF&BS those categories in which all persons present
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problems are b740 Muscle endurance functions, b735 Muscle tone functions,
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b620 Urinary functions and b280 Sensation of pain. Only those persons with
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high global levels of impairment will present problems in respiration, emotional
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functions, more specific urinary functions, and functions related with the
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hematological system. These results are consistent with clinical experience 29.
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In the A&P scale, d435 Moving objects with lower extremities, d455 Moving
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around, d460 Moving around in different locations and d450 Walking at the
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lowest levels of the continuum with a gap to the next category, namely d420
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Transferring oneself (see Figure 2). While those four ICF categories require the
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mobility of lower limbs, d420 Transferring oneself also requires the use of the
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arms. It is evident that persons with SCI will have problems in those ICF
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categories. One might, therefore, consider excluding these ICF categories from
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a clinical measure especially when only a dichotomous scale is used. This
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would improve the continuity of the scale as well as the distribution of the
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person abilities.
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The misfit of certain ICF categories may be related to the fact that our data is
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dichotomous. Ordinal response options with more than 2 categories allow a
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more precise differentiation among levels of functioning and probably would
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contribute to better fit statistics. Also, ICF categories may not always be
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interpreted in the same way by different health professionals. It could be that
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despite the standardized training of the interviewers and standardized
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interviewing protocol, the ICF categories have been interpreted differently by
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the health professionals collecting the data30.
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The results also show that some ICF categories are locally dependent (Figure 3
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& Figure 4) indicating that they address a similar content. To avoid
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redundancies when measuring functioning in SCI with an ICF-based clinical
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measure, either only one of the LID ICF categories is operationalized or all of
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them combined in a testlet 31. In the latter all locally dependent ICF categories
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are operationalized as one, single item. For example, the response options of
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items addressing the ICF categories d510 Washing oneself, d530 Toileting,
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d520 Caring for body parts, and d540 Dressing may be aggregated to a more
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general “self-care” item.
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Regarding the ICF categories showing DIF, it is important to mention that there
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are two types of DIF: uniform and non-uniform 32. Our results refer to uniform
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DIF.
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In the A&P dimension, DIF is only found for the age group. Persons in the older
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group (41.2 years) reported more problems in d445 Hand and arm use and
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d520 caring for body parts, which can be explained with the general decline of
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muscle power and strength with age 33.
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Social, physical and attitudinal barriers as well as a lack of support 34 are
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commonly reported challenges for the reintegration to the labor market. The
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group below median reported more problems in d820 School Education, d840
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Apprenticeship, and d870 Economic self-sufficiency. This finding probably
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reflects the challenges of the return to education or to work 35 especially shortly
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after injury 9. This is consistent with the fact that the younger age group had a
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shorter time since injury (mean = 3.29 years and SD = 4.4) than older group
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(mean = 9.22 and SD = 12.54).
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In the BF&BS dimension, DIF was observed for both age and gender. The
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gender differences in b445 Respiratory muscle functions and s720 Structure of
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shoulders may be explained the higher prevalence of tetraplegia36, 37 in the male
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group (47% vs. 40%). The gender differences in b640 Sexual functions and
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b670 Sensations associated with genital and reproductive functions have been
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frequently reported in the literature 38, 39.
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The age differences for b430 Hematological system functions and s610
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Structure of urinary system are not surprising. Problems such as anemia and
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blood coagulation problems as well as problems in urinary and bladder
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functions are common with aging and increase with time since injury 40, 41. The
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higher amount of reported problems in b550 Thermoregulatory functions and
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b755 Involuntary movement reaction functions in the younger group cannot be
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explained by age alone, but rather by the higher number of incomplete and non-
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traumatic injuries in the older group. Furthermore, a more active lifestyle can be
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expected in the younger group and this could explain the higher amount of
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reported problems in these functions.
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The most suitable solution will be to allow different difficulty parameters in the
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two subgroups. This technique is commonly presented in the literature as “item
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split”42.
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Study limitations
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The results of this study and the validity of the ICF categories as measures for
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functioning in SCI have to be understood in the context of their limitations. First
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of all, even though our sample is large and collected in different countries, we
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cannot say what portion of the SCI population is represented. As the recently
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published WHO World Report on SCI recognizes only a small handful of
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countries, like the US, Canada, and Australia have reliable data available 43. In
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addition, we cannot exclude selection bias in our sample. The health
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professionals of each health center recruiting the participants were only advised
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to recruit 40 individuals with traumatic SCI in the early post-acute situation and
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40 individuals with SCI in the post-acute situation taking into consideration
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inclusion and exclusion criteria but without providing further specifications. Last
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but not least, since the data was collected in 14 countries and 16 study centers
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only dichotomous data was collected to increase its reliability. Nevertheless we
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are aware that this approach reduces the variability of the data.
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Future studies will include quantitative analyses of existing data. This step is
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currently being prepared in the context of a cohort study with persons with SCI
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which is being carried out in Switzerland44. Item banks for each of the ICF
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categories are thereby created to which additional data from other studies and
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countries can be added. Since the ICF is used as common reference framework
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comparison among data collected from different populations is possible 45. In
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terms of the concrete operationalization of ICF categories in form of items, the
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item banks will be used to select the questions that provide most reliable and
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valid data.
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Conclusion
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The results of this study show that there are still some challenges that have to
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be addressed when integrating the ICF categories relevant for SCI into clinical
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measures. First, there is some lack of measurement invariance in relation to
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age and gender, which will have to be solved by allowing the ICF categories to
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have different difficulties in different samples.
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Second, we question whether some ICF categories that are usually a problem
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for persons with SCI, should be kept when developing a clinical measure for
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SCI. Third, all insights gained should also be taken into account when
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developing items to operationalize ICF categories. This study, however, also
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emphasizes that the ICF categories included in the analyses and which have
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been selected in an elaborated process during previous studies capture the
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whole spectrum of functioning from low to high levels in two dimensions,
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BF&BS and A&P.
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11. Uhlig T, Lillemo S, Moe RH, Stamm T, Cieza A, Boonen A et al. Reliability of the ICF Core Set for rheumatoid arthritis 2007 [cited 66 (Uhlig) National Resource Center for Rehabilitation in Rheumatology, Department of Rheumatology, Diakonhjemmet Hospital, Postboks 23 Vinderen, N-0319 Oslo, Norway]. Available from: URL: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=emed8&NEWS=N&AN=200736 7505. 12. Hilfiker R, Obrist S, Christen G, Lorenz T, Cieza A. The use of the comprehensive International Classification of Functioning, Disability and Health Core Set for low back pain in clinical practice: a reliability study. Physiotherapy research international : the journal for researchers and clinicians in physical therapy 2009;14(3):147-66. 13. Alviar MJ, Olver J, Pallant JF, Brand C, de Steiger R, Pirpiris M et al. Can the ICF osteoarthritis core set represent a future clinical tool in measuring functioning in persons with osteoarthritis undergoing hip and knee joint replacement? Journal of rehabilitation medicine : official journal of the UEMS European Board of Physical and Rehabilitation Medicine 2012;44(11):955-61. 14. Alguren B, Bostan C, Christensson L, Fridlund B, Cieza A. A multidisciplinary crosscultural measurement of functioning after stroke: Rasch analysis of the brief ICF Core Set for stroke. Top Stroke Rehabil 2011;18 Suppl 1:573-86. 15. Prodinger B, Salzberger T, Stucki G, Stamm T, Cieza A. Measuring functioning in people with fibromyalgia (FM) based on the international classification of functioning, disability and health (ICF)--a psychometric analysis. Pain practice : the official journal of World Institute of Pain 2012;12(4):255-65. 16. Biering-Sorensen F, Scheuringer M, Baumberger M, Charlifue SW, Post MW, Montero F et al. Developing core sets for persons with spinal cord injuries based on the International Classification of Functioning, Disability and Health as a way to specify functioning. Spinal cord 2006;44(9):541-6. 17. Rasch G. Probabilistic models for some intelligence and attainment tests. Copenhagen: [s.n.]; 1960. 18. Adams RJ, Wilson M, Wang W-c. The Multidimensional Random Coefficients Multinomial Logit Model. Applied Psychological Measurement 1997;21(1):1-23. 19. Andrich D. An index of person separation in latent trait theory, the traditional KR.20 index, and the Guttman Scale response pattern. Educational Research and Perspectives Educational Research and Perspectives 1982;9:95–104 20. Wright BD, Stone, M.H. Best Test Design. Chicago: MESA PRESS; 1979. 21. McHorney CA, Tarlov AR. Individual-patient monitoring in clinical practice: are available health status surveys adequate? Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation 1995;4(4):293-307. 22. Smith AB, Rush R, Fallowfield LJ, Velikova G, Sharpe M. Rasch fit statistics and sample size considerations for polytomous data. BMC medical research methodology 2008;8:33. 23. Linacre JM, Wright BD. Dichotomous Infit and Outfit Mean-Square Fit Statistics / Chi-
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Square Fit Statistics. Rasch Measurement Transactions 1994;8(2):350. 24. Linacre JM. What do Infit and Outfit, Mean-square and Standardized mean? Rasch MeasurementTransactions 2002;16(2):878. 25. Yen W. Scaling peformance assessments: strategies for managing local item dependence. Journal of Educational Measurement 1993;30(3):187-213. 26. Fischer GH, Molenaar, I.W. Rasch Models Foundations, Recent Developments, and Applications. New York; 1995. 27. Mair P, Hatzinger, R. Extended Rasch modeling: The eRm package for the application of IRT models in R. Journal of Statistical Software 2007;20(9):1-20.
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28. Hochberg Y, Benjamini Y. More powerful procedures for multiple significance testing. Statistics in medicine 1990;9(7):811-8. 29. WHO. Chapter 4: Health care and rehabilitation needs. WHO International Perspectives on Spinal Cord Injury. Geneva: World Health Organization 2013. p 67-91.
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30. Starrost K, Geyh S, Trautwein A, Grunow J, Ceballos-Baumann A, Prosiegel M et al. Interrater reliability of the extended ICF core set for stroke applied by physical therapists. Phys Ther 2008;88(7):841-51. 31. Wang W-C, Wilson M. The Rasch Testlet Model. Applied Psychological Measurement 2005;29(2):126-49. 32. Wilson M. Objective measurement: theory into practice. New Jersey: Norwood; 1994. 33. John EB, Liu W, Gregory RW. Biomechanics of muscular effort: age-related changes. Medicine and science in sports and exercise 2009;41(2):418-25. 34. Bergmark L, Westgren N, Asaba E. Returning to work after spinal cord injury: exploring young adults' early expectations and experience. Disability and rehabilitation 2011;33(2526):2553-8. 35. Hwang M, Zebracki K, Chlan KM, Vogel LC. Longitudinal employment outcomes in adults with pediatric-onset spinal cord injury. Spinal cord 2014. 36. Eriks-Hoogland IE, de Groot S, Post MW, van der Woude LH. Correlation of shoulder range of motion limitations at discharge with limitations in activities and participation one year later in persons with spinal cord injury. Journal of rehabilitation medicine : official journal of the UEMS European Board of Physical and Rehabilitation Medicine 2011;43(3):210-5. 37. Schilero GJ, Radulovic M, Wecht JM, Spungen AM, Bauman WA, Lesser M. A Center's Experience: Pulmonary Function in Spinal Cord Injury. Lung 2014. 38. Sale P, Mazzarella F, Pagliacci MC, Agosti M, Felzani G, Franceschini M. Predictors of changes in sentimental and sexual life after traumatic spinal cord injury. Archives of physical medicine and rehabilitation 2012;93(11):1944-9. 39. Valtonen K, Karlsson AK, Siosteen A, Dahlof LG, Viikari-Juntura E. Satisfaction with sexual life among persons with traumatic spinal cord injury and meningomyelocele. Disability and rehabilitation 2006;28(16):965-76. 40. Drake MJ, Cortina-Borja M, Savic G, Charlifue SW, Gardner BP. Prospective evaluation of urological effects of aging in chronic spinal cord injury by method of bladder management. Neurourology and urodynamics 2005;24(2):111-6. 41. Beuret-Blanquart F, Boucand MH. [Aging with spinal cord injury]. Annales de readaptation et de medecine physique : revue scientifique de la Societe francaise de reeducation fonctionnelle de readaptation et de medecine physique 2003;46(9):578-91. 42. Cieza A, Hilfiker R, Boonen A, van der Heijde D, Braun J, Stucki G. Towards an ICF-based clinical measure of functioning in people with ankylosing spondylitis: a methodological exploration. Disability and rehabilitation 2009;31(7):528-37. 43. WHO. Chapter 2: A global picture of spinal cord injury. WHO International Perspectives on Spinal Cord Injury. Geneva: World Health Organization2013. p 11-41.
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44. Post MW, Brinkhof MW, von Elm E, Boldt C, Brach M, Fekete C et al. Design of the Swiss Spinal Cord Injury Cohort Study. American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 2011;90(11 Suppl 2):S5-16.
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45. Stucki G, Kostanjsek N, Ustun B, Cieza A. ICF-based classification and measurement of functioning. European journal of physical and rehabilitation medicine 2008;44(3):315-28.
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Table 1: Sociodemographic and injury related characteristics of the participants for the whole sample
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and by resources of the country.
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Figure 1: Person Item Map Body Functions and Body Structures
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Figure 2: Person Item Map Activity and Participation
Table 2: Rasch estimated difficulties, Standard Error (SE) and difficulty ranking for the ICF categories of the Body Functions and Body Structures (BF&BS) dimension, with indication of presence of misfit, Local Item Dependence (LID) and Differential Item Functioning (DIF). ICF categories from the Brief ICF Core Sets are marked with ‘c’, those from the statistical selection with ‘°’ and those which are a problem for more than 90% of the participants with ‘+’.
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Table 3: Rasch estimated difficulties, Standard Error (SE) and difficulty ranking for the ICF categories of the Activity and Participation (A&P) dimension, with indication of presence of misfit, Local Item Dependence (LID) and Differential Item Functioning (DIF). ICF categories from the Brief ICF Core Sets are marked with ‘c’, those from the statistical selection with ‘°’ and those which are a problem for more than 90% of the participants with ‘+’.
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Figure 3: Local item dependences (LID) in the ICF categories in the Body function and Body Structure
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(BF&BS) dimensions
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Figure 4: Local item dependences (LID) in the ICF categories in the Activity and Participation (A&P) dimensions
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Age Years of formal education Situation (early post-acute)
187 158 208 332 87 300 408
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208 58 62 46
12 39 220 106 37 16 38 Mean (SD ) 4.5 (6.8 )
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Time since injury
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Injury Related
SCI level (tetraplegia) AIS impairment (complete) Bony vertebral injury (yes) Associated injury (yes) Spinal surgery (yes) Ventilatory assistance within last 24 hours (no) Asia Impairment Scale A B C D Injury Etiology Sports Assault Transportation Fall Other traumatic cause Non-traumatic spinal cord dysfunction Unspecified or unknown
44.0 37.2 55.6 78.9 20.8 70.8 99.0
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Socio-Demographic
Gender (male) Current marital status (married) Living alone (yes) Current occupation (Paid or Self-Employed)
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Characteristics
High Resource Countries Frequency % 623 59.4 484 77.7 278 45.0 160 25.8 256 41.1 Mean (SD ) 45 (15.8 ) 13.6 (3.9 ) Frequency %
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Low Resource Countries Frequency % 425 40.6 328 77.2 197 46.4 24 5.7 199 46.8 Mean (SD ) 37.9 (12.6 ) 9.7 (4.3 ) Frequency %
55.6 15.5 16.6 12.3
2.8 9.2 51.8 24.9 8.7 3.8 8.9
All Frequency 1048 812 475 184 455 Mean (SD ) 42.2 (15. ) 12.1 (4.5 ) Frequency
% 100 77.5 45.5 17.6 43.4
%
302 317 277 448 178 472 603
48.5 50.9 49.9 72.6 29.2 76.5 97.4
489 475 485 780 265 772 1011
46.7 45.3 52.2 75.1 25.8 74.2 98.1
277 60 106 112
49.9 10.8 19.1 20.2
485 118 168 158
52.2 12.7 18.1 17.0
68 29 214 117 78 112 88 Mean (SD ) 7.5 (11.4)
10.9 4.7 34.3 18.8 12.5 18.0 14.1
80 68 434 223 115 128 125 Mean (SD ) 6.2 (9.9)
7.6 6.5 41.4 21.3 11.0 12.2 11.9
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Differential Item Functioning (DIF)
Dimension: Body Functions and Body Structures (BF&BS )
o c o o o c o o c o o o c,o c,o o c,o o c,+ + + o o o c,o o c,o c,o o c,o
Infit MSQ
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c,o
0 1.74 1.08 2.27 -2.15 -2.19 2.64 1.24 3.27 2.04 0.58 0.33 -2.03 1.24 0.46 2.29 -2.37 -1.63 -1.36 -0.63 -0.11 -2.57 -3.23 -1.99 -1.55 -1.69 -1.96 0.67 -0.81 2.05 0.86 1.51 0.14
Outfit MSQ
1.49 1.35 1.15 1.37 0.79 0.73 0.93 0.87 1.25 0.77 0.73 0.76 0.74 0.96 0.87 0.98 0.86 1.02 1.18 0.85 1.04 0.68 1.08 0.82 0.97 1.07 0.72 1.16 1.08 0.89 0.93 1.05 1.80 1 3.03%
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Temperament and personality functions Energy and drive functions Sleep functions Emotional functions Sensory functions related to temperature and other stimuli Sensation of pain Blood vessel functions Blood pressure functions Haematological system functions Respiration functions Respiratory muscle functions Exercise tolerance functions Defecation functions Weight maintenance functions Thermoregulatory functions Urinary excretory functions Urination functions Sexual functions Sensations associated with genital and reproductive functions Mobility of joint functions Stability of joint functions Muscle tone functions Muscle endurance functions Motor reflex functions Involuntary movement reaction functions Control of voluntary movement functions Sensations related to muscles and movement functions Protective functions of the skin Sensation related to the skin Structure of respiratory system Structure or urinary system Structure of shoulder region Structure of areas of skin Number of significant ICF-categories Percentage of significant ICF-categories
Rank SE1 Item Difficulty2 Difficulty 0 16 0.08 27 0.07 23 0.09 30 0.1 5 0.1 4 0.1 32 0.08 24 0.13 33 0.09 28 0.07 20 0.07 18 0.1 6 0.08 24 0.07 19 0.09 31 0.11 3 0.09 10 0.08 12 0.07 14 0.07 15 0.11 2 0.14 1 0.09 7 0.08 11 0.09 9 0.09 8 0.07 21 0.07 13 0.09 29 0.07 22 0.08 26 0.07 17
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b126 b130 b134 b152 b270 b280 b415 b420 b430 b440 b445 b455 b525 b530 b550 b610 b620 b640 b670 b710 b715 b735 b740 b750 b755 b760 b780 b810 b840 s430 s610 s720 s810
Title
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ICF-code
Item Difficulty
1.20 1.13 1.08 1.17 0.81 0.84 0.90 0.84 0.97 0.84 0.80 0.84 0.93 0.98 0.89 1.03 0.97 0.96 1.02 0.94 1.01 0.88 0.99 0.86 0.97 1.04 0.86 1.13 1.03 0.85 0.93 0.86 1.13 0
LID
Gender
Age
X X X X X
X X X
X
X X X X
X X
X X X X
X
X X X X X 17 51.52%
4 12.12%
4 12.12%
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SE = Standard Error Increasing rank, decreasing probability for a problem
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Differential Item Functioning (DIF)
Dimension: Activity and Participation (A&P )
0.99 1.09 1.73 0.75 0.78 0.64 0.99 0.89 1.13 1.37 0.72 1.11 1.10 1.08 0.52 0.55 0.60 0.65 0.65 0.62 0.68 1.04 0.74 0.99 1.43 2.06 1.24 1.46 1.26 1.25 1.97
Infit MSQ
LID 0.98 1.06 1.18 0.87 0.87 0.76 1.00 0.89 1.10 1.05 0.95 1.03 1.08 1.08 0.68 0.70 0.74 0.75 0.78 0.77 0.82 1.04 0.88 1.06 1.22 1.07 1.14 1.17 1.17 1.06 1.17
3 9.68%
Gender
0
Age
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16 25 29 27 6 5 1 18 4 2 3 10 9 14 11 12 7 8 23 26 19 17 13 15 24 31 28 21 22 20 30
Outfit MSQ
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0 1.28 1.75 1.69 -1.29 -1.34 -3.39 0.48 -2.87 -3.31 -3.1 -1.01 -1.02 -0.35 -0.81 -0.55 -1.07 -1.04 1.1 1.32 0.59 0.05 -0.55 -0.19 1.28 3.06 1.72 0.84 0.9 0.61 2.39
Rank Difficulty2
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SE1 Item Difficulty 0.00 0.08 0.08 0.08 0.09 0.09 0.14 0.07 0.12 0.14 0.13 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.07 0.08 0.07 0.07 0.08 0.08 0.08 0.11 0.08 0.07 0.07 0.07 0.09
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Acquiring skills Carrying out daily routine c,o Handling stress and other psychological demands o Using communication devices and techniques c Changing basic body position c Transferring oneself + Moving objects with lower extremities c,o Hand and arm use c Walking c,+ Moving around + Moving around in different locations c,o Moving around using equipment c Using transportation o Driving c Washing oneself c,o Caring for body parts c,o Toileting c Dressing c Eating c Drinking o Looking after one's health o Acquisition of goods and services o Preparing meals o Assisting others o Intimate relationships o School education o Apprenticeship (work preparation) o Acquiring, keeping and terminating a job o Economic self-sufficiency o Community life o Religion and spirituality Number of significant ICF-categories Percentage of significant ICF-categories 1 SE = Standard Error 2 Increasing rank, decreasing probability for a problem d155 d230 d240 d360 d410 d420 d435 d445 d450 d455 d460 d465 d470 d475 d510 d520 d530 d540 d550 d560 d570 d620 d630 d660 d770 d820 d840 d845 d870 d910 d930
Item Difficulty
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X X X X X X
X
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X X
X X
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15 48.39%
0 0.00%
5 16.13%
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Person Parameter Distribution
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b740 Muscle endurance functions b735 Muscle tone functions b620 Urination functions b280 Sensation of pain b270 Sensory functions related to temperature and other stimuli b525 Defecation functions b750 Motor reflex functions b780 Sensations related to muscles and movement functions b760 Control of voluntary movement functions b640 Sexual functions b755 Involuntary movement reaction functions b670 Sensations associated with genital and reproductive functions b840 Sensation related to the skin b710 Mobility of joint functions b715 Stability of joint functions s810 Structure of areas of skin b455 Exercise tolerance functions b550 Thermoregulatory functions b445 Respiratory muscle functions b810 Protective functions of the skin s610 Structure or urinary system b134 Sleep functions b420 Blood pressure functions b530 Weigth maintenance functions s720 Structure of shoulder region b130 Energy and drive functions b126 Temperament and personality functions b440 Respiration functions s430 Structure of respiratory system b152 Emotional functions b610 Urinary excretory functions b415 Blood vessel functions b430 Haematological system functions
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Person Item Map
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d435 Moving objects with lower extremities d455 Moving around d460 Moving around in different locations d450 Walking d420 Transferring oneself d410 Changing basic body position d530 Toileting d540 Dressing d470 Using transportation d465 Moving around using equipment d510 Washing oneself d520 Caring for body parts d630 Preparing meals d475 Driving d660 Assisting others d620 Acquisition of goods and services d445 Hand and arm use d570 Looking after one's health d910 Community life d845 Acquiring, keeping and terminating a job d870 Economic self−sufficiency d550 Eating d770 Intimate relationships d230 Carrying out daily routine d560 Drinking d360 Using communication devices and techniques d840 Apprenticeship (work preparation) d240 Handling stress and other psychological demands d930 Religion and spirituality d155 Acquiring skills d820 School education
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S0003-9993(14)00398-0
DOI:
10.1016/j.apmr.2014.05.006
Reference:
YAPMR 55842
To appear in:
ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION
Received Date: 23 January 2014 Revised Date:
6 May 2014
Accepted Date: 9 May 2014
Please cite this article as: Ballert CS, Stucki G, Biering-Sørensen F, Cieza A, Towards the development of clinical measures for spinal cord injury based on the International Classification of Functioning, Disability and Health with Rasch analyses, ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION (2014), doi: 10.1016/j.apmr.2014.05.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Full title: Towards the development of clinical measures for spinal cord injury based on the International Classification of Functioning, Disability and Health with Rasch analyses
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Running head: Psychometric properties of ICF categories for functioning in SCI
Authors: Msc Dpl Stat Carolina S. Ballert1,2,3, Prof Gerold Stucki1,2,3, Prof Fin Biering-
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Sørensen4, Prof Alarcos Cieza1,5,6
Swiss Paraplegic Research (SPF), Nottwil, Switzerland
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Department of Health Sciences and Health Policy, University of Lucerne
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ICF Research Branch of WHO Collaborating Center for the Family of International Classifications in
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German
Clinic for Spinal Cord Injuries, Glostrup Hospital and Faculty of Health and Medical Sciences,
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University of Copenhagen, Copenhagen, Denmark Faculty of Social and Human Sciences, School of Psychology, University of Southampton, UK
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Department of Medical Informatics, Biometry and Epidemiology – IBE, Chair for Public Health and
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Health Services Research, Research Unit for Biopsychosocial Health, Ludwig-Maximilians-University (LMU), Munich, Germany
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Acknowledgements: The author wants to thank Ursula Ludgate, Alan Tennant, and
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Bernd Fellinghauer for their valuable input, feed-backs and support.
Conflict of interest:
Corresponding author & Request for Reprints :
Faculty of Social and Human Sciences School of Psychology
Highfield Campus Southampton SO17 1BJ
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University of Southampton
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Telephone: +44 23 8059 7549 Facsimile: +44 23 8059 4597
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Professor Alarcos Cieza
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The authors declare no conflict of interest.
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Full title: Towards the development of clinical measures for spinal cord injury
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based on the International Classification of Functioning, Disability and Health
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with Rasch analyses
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Running head: Psychometric properties of ICF categories for functioning in SCI
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Abstract:
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Objectives: To determine whether ICF categories relevant to SCI can be
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integrated in clinical measures and get insights to guide their future
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operationalization. Specific aims are to find out whether the ICF categories
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relevant to SCI [1] fit a Rasch model taking into consideration the dimensionality
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found in previous investigations, [2] show local item dependencies (LID), or [3]
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differential item functioning (DIF).
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Design: All second level ICF categories collected in ‘Development of ICF Core
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Sets for SCI’ project in specialized centers within fourteen countries from 2006-
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2008.
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Setting: Secondary data analysis
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Participants: 1048 adults with SCI from the early post-acute and the long-term
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living context.
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Interventions: n.a.
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Main Outcome Measures: Two unidimensional Rasch analyses one for the
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ICF categories from body functions and body structures components and
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another for the ICF categories from the activities and participation component.
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Results: [1] Results support good reliability and targeting of the ICF categories in both dimensions. In each dimension few ICF categories were subject to
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misfit. [2] Local item dependency was observed between ICF categories of
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same chapters, [3] and group effects for age and gender only to a small extent.
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Conclusion: The validity of ICF categories to develop measures of functioning
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in SCI for clinical practice and research is to some extent supported. Model
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adjustments were suggested to further improve their operationalization and
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psychometrics.
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Keywords: ICF, Paraplegia, Tetraplegia, Spinal Cord Injuries, IRT, Rasch
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Abbreviations: ICF (International Classification of Functioning, Disability and
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Health), WHO (World Health Organization), SCI (spinal cord injury), LID (local
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item dependence), DIF (differential item functioning), BF (body functions), BS
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(body structures), A&P (activities and participation), EF (environmental factors),
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PSI (persons separation index), KR-20 (Kuder-Richardson formula 20), SD
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(standard deviation), SE (standard error).
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INTRODUCTION
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The International Classification of Functioning, Disability and Health (ICF)
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provides a unified language and framework to describe human functioning and
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its external, environmental influences 1. The ICF has been introduced by the
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World Health Organisation (WHO) to improve the data collection and their
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comparability across patients, institutions, settings and countries.
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The ICF is organized in a hierarchical structure starting from the most general
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component level including body functions, coded with the letter b-, body
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structures, coded s-, activities and participation, coded d-, and environmental
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factors, coded e-. In the components, the chapters are included and coded with
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a number in addition to the letter of the component (e.g. b2 Sensory functions
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and pain). The chapters are further specified with second, third and fourth level
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categories which are coded by adding two, three or four digits to the chapter
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(e.g. b280 Sensation of pain, b2801 Pain in body part, and b28014 Pain in
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upper limb). With a rating scale called “qualifier scale” the level of impairment or
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difficulty in each ICF category can be indicated on a five level rating scale from
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0 to 4. With both, the categories and qualifiers, the ICF has been used for the
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description and the assessment of functioning.
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However, the development of valid clinical measures needs to include a number
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of steps which range from the selection of domains, the testing of their
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dimensionality and their psychometric properties to their operationalization with
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items or clinical tests, and final testing of their psychometric properties. In the
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field of spinal cord injury (SCI) different steps have already been carried out.
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First, Brief and Comprehensive ICF Core Sets for individuals with SCI in the
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early post-acute and the long-term phase have been developed. This took place
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in a consensus conference using evidence from preliminary studies. When
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implementing them in clinical practice, the Brief ICF Core Sets are the starting
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points. The Comprehensive ICF Core Sets represent the pool from which
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additional ICF categories can be selected if relevant for the patient. This
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approach facilitates the implementation of the ICF in clinical practice 2. In a
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follow-up study, we identified ICF categories from the Comprehensive Core
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Sets for SCI 3, 4 that best differentiate among different levels of self-reported
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health 5 and tested the robustness of the dimensionality of those ICF categories
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together with those of the Brief ICF Core Sets.
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In this study we will concentrate on the psychometric properties of the ICF
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categories, since this can also provide insights for their operationalization. We
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build, thereby, on knowledge gathered from previous studies with ICF Core Sets
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in which clinical measures of functioning were developed6-15. The psychometric
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analysis will allow to determine whether the ICF categories relevant for SCI can
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be used as a clinical measure and also guide the selection of items, in case of
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the development of a patient reported questionnaire. For example, if an ICF
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category has two different levels of difficulty in subgroups (e.g. males and
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females), group specific items are probably needed for further operationalization
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of that ICF category.
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The overall objectives of this investigation are to determine whether the ICF
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categories relevant to SCI can be integrated in clinical measures and get
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insights to guide the future operationalization with items of those ICF
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categories.
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The specific aims are to find out whether [1] the ICF categories relevant to SCI
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fit the Rasch model taking into consideration the dimensionality found in
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previous investigations, i.e. body functions (BF) and body structures (BS) as
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one dimension and activities and participation (A&P) as a second dimension, [2]
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the ICF categories show local item dependencies (LID), or [3] differential item
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functioning (DIF).
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Study Design
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Explorative psychometric study using data collected in a cross-sectional, multi-
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center study carried out in the international project ‘Development of ICF Core
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Sets for Spinal Cord Injury’ in sixteen SCI specialized centers within fourteen
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countries from 2006-2008. Persons with traumatic SCI, > 18 years, who
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understood the purpose of the study and signed informed consent, were
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included. Only persons with traumatic brain injury or having been diagnosed
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with a mental disorder prior to the SCI were excluded. The clinical and
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sociodemographic information collected and exclusively used to describe the
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study population are shown in Table 1. Participants did not receive any
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incentive to participate.
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Data collection was approved by the ethics committees in charge of the study
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centers involved and performed in accordance with the Declaration of Helsinki.
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Study Population
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A total of 1048 persons with SCI participated in this study; 489 from the early
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post-acute and 559 from the long-term context (Table 1). Four hundred and
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twenty five participants were citizens of middle/low resource countries
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(Malaysia, South Africa, Brazil, Thailand, India and Vietnam) and 623 from high
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resource countries (USA, Switzerland, Denmark, Canada, Australia, Germany,
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New Zealand and Israel).
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Data Collection
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After having collected the clinical and demographic information, professionals
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collected data using a checklist containing all second-level categories of the ICF
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(N = 264). The impairment/difficulty in the ICF categories was recorded
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dichotomously; with 1 indicating an impairment/difficulty. Additional information
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about data collection procedures can be found elsewhere16.
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The focus of this study is on ICF categories describing functioning in SCI, i.e.
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ICF categories of BF&BS and A&P. We included in the analyses the ICF
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categories from the Brief Core Set for SCI for the early post-acute and long-
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term context and statistically selected ICF categories that best capture levels of
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patients’ and health professionals’ reported general health of persons with SCI
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in the early post-acute and long-term living context 5. ICF categories that were a
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problem for more than 90% of the participants were also included. This made
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up in total 64 ICF categories (29 BF, 4 BS and 31 A&P). It is important to
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emphasize that ratings of the ICF categories and not items developed to
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measure them are used in these analyses.
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All included ICF categories are shown in the first two columns of Table 2 and 3.
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The ICF categories of the Brief ICF Core Sets selected by experts are marked
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with ‘c’, those coming from the statistical selection with ‘°’ and those which
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represent a problem for more than 90% of the participants with ‘+’.
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Statistical Analysis
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Unidimensional Rasch analyses 17 were used to determine the models fit and
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the psychometric properties of the ICF categories selected for this study. We
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opted for unidimensional Rasch because the presence of these two dimensions
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had already been identified in a previous study based on multi-dimensional
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Rasch18. The dimensions that we intended to capture are “impairment in body
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functions” and “difficulties in activities and participation domains”.
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The Rasch model provides an item and a person estimate. The estimate of the
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person is called the persons’ ability and tells about the ranking of each person
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on the dimensions’ continuum. The estimate of the item is called the item
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difficulty and informs about the position of the item in the same continuum.
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The models’ reliabilities were assessed using the KR-20 index and the person
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separation index (PSI). They inform about the internal consistency of the Rasch
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estimates 19 and are interpreted in the same way as a Cronbach’s alpha 20.
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A good targeting is achieved when the spectrum of difficulties of the ICF
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categories match the abilities of the persons. Furthermore, a scale is free of
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ceiling and floor effects when less than 15% of the persons’ abilities exceed the
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most difficult ICF category and less than 15% of the persons’ abilities are below
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the easiest ICF category 21. The quality of the coverage of the ICF categories on
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the measurement continuum will be illustrated with the person-item map, which
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displays a visual ruler of the estimated ICF category difficulties and the
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frequency of persons with the associated level of ability. Persons’ ability
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histograms are expected to be bell-shaped.
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A good item fit is achieved when the observed data are close to the expected
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data. The items’ fit is provided by the outfit and infit mean squared errors22. An
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item`s goodness and its usability for measurement is confirmed when the mean
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squared infit and outfit are between 0.5 and 1.5
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the pattern of responses. Outfit is more sensitive to responses to items with
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difficulty far from a person.
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Local Item Dependency (LID) assumption was verified with a correlational
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analysis of the standardized residuals of the Rasch analysis 25. High
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correlations (|r|>0.3) indicate LID between two ICF categories.
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The Differential Item Functioning (DIF) testing included groups of age (below
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and above the median age 41.2 years) and gender, and used the Wald test to
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compare Rasch parameters of each ICF category by group 26.
. Infit is more sensitive to
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All Rasch analyses were performed with the R-package eRm 27. Instead of
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setting the average item difficulties to zero, we restricted the first item to be
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zero, which is the default setting in this package. Benjamini-Hochberg
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correction for multiple testing, controlling the false detection rate, was applied
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for the p-values of the ICF categories’ DIF analysis 28 because the same
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person’s ratings were submitted twice to the DIF analysis for each of the 2
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different sub-groups (age and gender).
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Results
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The sociodemographic and clinical characteristics of the participants are
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presented in Table 1. High resource countries show a higher prevalence of
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persons with tetraplegia (50.9% vs. 37.2%), more persons living alone (25.8%
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vs. 5.7%), less transportation accidents (51.8% vs. 34.3%), and more non-
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traumatic spinal cord dysfunctions (38% vs. 18%).
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A total of 33 ICF categories were included in the analyses of the dimension
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BF&BS and 31 in the dimension of A&P. The first Rasch analysis for each
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dimension detected misfitting persons (person infit statistic |θ|>2.5), which were
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excluded. The following analyses were carried out with 1036 participants in the
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BF&BS dimension and 1020 participants in the A&P dimension.
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Model fit
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The estimates for the internal consistency indicate a good to excellent reliability
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of the Rasch models (BF&BS: KR-20=0.85 and PSI=0.86; A&P: KR-20=0.90
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and PSI=0.89).
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The ICF categories’ difficulties are well-targeted on the persons’ abilities. In the
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BF&BS dimension the mean ICF category difficulty was -0.06 (SD=1.79) and
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the mean person ability 0.10 (SD=1.29). For the A&P dimension the mean ICF
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category difficulty was -0.09 (SD=1.65) and the mean person ability 0.29
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(SD=1.56). The person-item maps on Figure 1 and 2 show that the continuum
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of the scale is well addressed for the BF&BS dimension, but the A&P dimension
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presents a gap of more than 1.5 logit from d450 Walking to d420 Transferring
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oneself. In both dimensions, the increases in difficulty on the continuum
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included 18% of logit changes ≤0.05 for the BF&BS and 35% for the A&P ICF
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categories. This indicates that the measurement continuum could be addressed
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with fewer ICF categories than available. Ceiling or floor effects were not
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observed.
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Fit of the ICF categories
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Table 2 and 3 present the results of the psychometric investigation of the ICF
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categories with their difficulties, the standard error (SE), and the difficulty rank
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for the BF&BS and A&P dimensions respectively. In addition, Table 2 reports
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the infit and outfit MSQ statistics.
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All categories of BF&BS present infit statistics between 0.5 and 1.5 and only
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one shows outfit statistics above 1.5, namely s810 structure of areas of skin.
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Also, in the A&P dimension, all infit statistics lie between 0.5 and 1.5. Three
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A&P categories, however, show outfit statistics above 1.5, namely d240
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Handling stress and other psychological demands, d820 School education, and
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d930 Religion and spirituality.
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ICF categories with outfit statistics above 1.5 indicate categories which under-
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discriminate, i.e. they do not differentiate well different levels of the continuum.
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The columns entitled LID of Table 2 and 3 indicate the locally dependent ICF
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categories. Further, the 17 ICF categories of BF&BS showing LID are depicted
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graphically in Figure 3 while those 15 from A&P in Figure 4. In general, ICF
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categories show local dependencies with others from the same chapter and
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with those with which they are related from a functional point of view, e.g. b810
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Protective functions of the skin and s810 Structure of areas of skin.
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The ICF categories with DIF for age and gender are presented in Table 2 and 3.
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In the A&P dimension, no DIF is found for gender and for five ICF categories in
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the age group (16.13%). In the BF&BS dimension, age and gender groups
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counted respectively 4 (12.12%) ICF categories with DIF.
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Discussion
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The results of this investigation show the validity of the ICF categories relevant
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for SCI to capture the whole spectrum of functioning from low to high levels in
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two dimensions.
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In both dimensions there is an intuitive and meaningful progression in the order
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of ICF categories. In BF&BS those categories in which all persons present
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problems are b740 Muscle endurance functions, b735 Muscle tone functions,
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b620 Urinary functions and b280 Sensation of pain. Only those persons with
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high global levels of impairment will present problems in respiration, emotional
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functions, more specific urinary functions, and functions related with the
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hematological system. These results are consistent with clinical experience 29.
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In the A&P scale, d435 Moving objects with lower extremities, d455 Moving
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around, d460 Moving around in different locations and d450 Walking at the
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lowest levels of the continuum with a gap to the next category, namely d420
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Transferring oneself (see Figure 2). While those four ICF categories require the
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mobility of lower limbs, d420 Transferring oneself also requires the use of the
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arms. It is evident that persons with SCI will have problems in those ICF
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categories. One might, therefore, consider excluding these ICF categories from
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a clinical measure especially when only a dichotomous scale is used. This
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would improve the continuity of the scale as well as the distribution of the
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person abilities.
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The misfit of certain ICF categories may be related to the fact that our data is
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dichotomous. Ordinal response options with more than 2 categories allow a
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more precise differentiation among levels of functioning and probably would
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contribute to better fit statistics. Also, ICF categories may not always be
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interpreted in the same way by different health professionals. It could be that
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despite the standardized training of the interviewers and standardized
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interviewing protocol, the ICF categories have been interpreted differently by
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the health professionals collecting the data30.
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The results also show that some ICF categories are locally dependent (Figure 3
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& Figure 4) indicating that they address a similar content. To avoid
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redundancies when measuring functioning in SCI with an ICF-based clinical
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measure, either only one of the LID ICF categories is operationalized or all of
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them combined in a testlet 31. In the latter all locally dependent ICF categories
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are operationalized as one, single item. For example, the response options of
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items addressing the ICF categories d510 Washing oneself, d530 Toileting,
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d520 Caring for body parts, and d540 Dressing may be aggregated to a more
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general “self-care” item.
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Regarding the ICF categories showing DIF, it is important to mention that there
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are two types of DIF: uniform and non-uniform 32. Our results refer to uniform
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DIF.
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In the A&P dimension, DIF is only found for the age group. Persons in the older
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group (41.2 years) reported more problems in d445 Hand and arm use and
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d520 caring for body parts, which can be explained with the general decline of
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muscle power and strength with age 33.
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Social, physical and attitudinal barriers as well as a lack of support 34 are
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commonly reported challenges for the reintegration to the labor market. The
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group below median reported more problems in d820 School Education, d840
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Apprenticeship, and d870 Economic self-sufficiency. This finding probably
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reflects the challenges of the return to education or to work 35 especially shortly
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after injury 9. This is consistent with the fact that the younger age group had a
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shorter time since injury (mean = 3.29 years and SD = 4.4) than older group
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(mean = 9.22 and SD = 12.54).
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In the BF&BS dimension, DIF was observed for both age and gender. The
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gender differences in b445 Respiratory muscle functions and s720 Structure of
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shoulders may be explained the higher prevalence of tetraplegia36, 37 in the male
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group (47% vs. 40%). The gender differences in b640 Sexual functions and
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b670 Sensations associated with genital and reproductive functions have been
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frequently reported in the literature 38, 39.
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The age differences for b430 Hematological system functions and s610
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Structure of urinary system are not surprising. Problems such as anemia and
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blood coagulation problems as well as problems in urinary and bladder
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functions are common with aging and increase with time since injury 40, 41. The
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higher amount of reported problems in b550 Thermoregulatory functions and
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b755 Involuntary movement reaction functions in the younger group cannot be
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explained by age alone, but rather by the higher number of incomplete and non-
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traumatic injuries in the older group. Furthermore, a more active lifestyle can be
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expected in the younger group and this could explain the higher amount of
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reported problems in these functions.
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The most suitable solution will be to allow different difficulty parameters in the
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two subgroups. This technique is commonly presented in the literature as “item
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split”42.
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Study limitations
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The results of this study and the validity of the ICF categories as measures for
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functioning in SCI have to be understood in the context of their limitations. First
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of all, even though our sample is large and collected in different countries, we
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cannot say what portion of the SCI population is represented. As the recently
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published WHO World Report on SCI recognizes only a small handful of
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countries, like the US, Canada, and Australia have reliable data available 43. In
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addition, we cannot exclude selection bias in our sample. The health
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professionals of each health center recruiting the participants were only advised
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to recruit 40 individuals with traumatic SCI in the early post-acute situation and
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40 individuals with SCI in the post-acute situation taking into consideration
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inclusion and exclusion criteria but without providing further specifications. Last
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but not least, since the data was collected in 14 countries and 16 study centers
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only dichotomous data was collected to increase its reliability. Nevertheless we
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are aware that this approach reduces the variability of the data.
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Future studies will include quantitative analyses of existing data. This step is
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currently being prepared in the context of a cohort study with persons with SCI
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which is being carried out in Switzerland44. Item banks for each of the ICF
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categories are thereby created to which additional data from other studies and
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countries can be added. Since the ICF is used as common reference framework
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comparison among data collected from different populations is possible 45. In
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terms of the concrete operationalization of ICF categories in form of items, the
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item banks will be used to select the questions that provide most reliable and
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valid data.
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Conclusion
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The results of this study show that there are still some challenges that have to
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be addressed when integrating the ICF categories relevant for SCI into clinical
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measures. First, there is some lack of measurement invariance in relation to
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age and gender, which will have to be solved by allowing the ICF categories to
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have different difficulties in different samples.
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Second, we question whether some ICF categories that are usually a problem
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for persons with SCI, should be kept when developing a clinical measure for
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SCI. Third, all insights gained should also be taken into account when
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developing items to operationalize ICF categories. This study, however, also
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emphasizes that the ICF categories included in the analyses and which have
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been selected in an elaborated process during previous studies capture the
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whole spectrum of functioning from low to high levels in two dimensions,
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BF&BS and A&P.
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11. Uhlig T, Lillemo S, Moe RH, Stamm T, Cieza A, Boonen A et al. Reliability of the ICF Core Set for rheumatoid arthritis 2007 [cited 66 (Uhlig) National Resource Center for Rehabilitation in Rheumatology, Department of Rheumatology, Diakonhjemmet Hospital, Postboks 23 Vinderen, N-0319 Oslo, Norway]. Available from: URL: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=emed8&NEWS=N&AN=200736 7505. 12. Hilfiker R, Obrist S, Christen G, Lorenz T, Cieza A. The use of the comprehensive International Classification of Functioning, Disability and Health Core Set for low back pain in clinical practice: a reliability study. Physiotherapy research international : the journal for researchers and clinicians in physical therapy 2009;14(3):147-66. 13. Alviar MJ, Olver J, Pallant JF, Brand C, de Steiger R, Pirpiris M et al. Can the ICF osteoarthritis core set represent a future clinical tool in measuring functioning in persons with osteoarthritis undergoing hip and knee joint replacement? Journal of rehabilitation medicine : official journal of the UEMS European Board of Physical and Rehabilitation Medicine 2012;44(11):955-61. 14. Alguren B, Bostan C, Christensson L, Fridlund B, Cieza A. A multidisciplinary crosscultural measurement of functioning after stroke: Rasch analysis of the brief ICF Core Set for stroke. Top Stroke Rehabil 2011;18 Suppl 1:573-86. 15. Prodinger B, Salzberger T, Stucki G, Stamm T, Cieza A. Measuring functioning in people with fibromyalgia (FM) based on the international classification of functioning, disability and health (ICF)--a psychometric analysis. Pain practice : the official journal of World Institute of Pain 2012;12(4):255-65. 16. Biering-Sorensen F, Scheuringer M, Baumberger M, Charlifue SW, Post MW, Montero F et al. Developing core sets for persons with spinal cord injuries based on the International Classification of Functioning, Disability and Health as a way to specify functioning. Spinal cord 2006;44(9):541-6. 17. Rasch G. Probabilistic models for some intelligence and attainment tests. Copenhagen: [s.n.]; 1960. 18. Adams RJ, Wilson M, Wang W-c. The Multidimensional Random Coefficients Multinomial Logit Model. Applied Psychological Measurement 1997;21(1):1-23. 19. Andrich D. An index of person separation in latent trait theory, the traditional KR.20 index, and the Guttman Scale response pattern. Educational Research and Perspectives Educational Research and Perspectives 1982;9:95–104 20. Wright BD, Stone, M.H. Best Test Design. Chicago: MESA PRESS; 1979. 21. McHorney CA, Tarlov AR. Individual-patient monitoring in clinical practice: are available health status surveys adequate? Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation 1995;4(4):293-307. 22. Smith AB, Rush R, Fallowfield LJ, Velikova G, Sharpe M. Rasch fit statistics and sample size considerations for polytomous data. BMC medical research methodology 2008;8:33. 23. Linacre JM, Wright BD. Dichotomous Infit and Outfit Mean-Square Fit Statistics / Chi-
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Square Fit Statistics. Rasch Measurement Transactions 1994;8(2):350. 24. Linacre JM. What do Infit and Outfit, Mean-square and Standardized mean? Rasch MeasurementTransactions 2002;16(2):878. 25. Yen W. Scaling peformance assessments: strategies for managing local item dependence. Journal of Educational Measurement 1993;30(3):187-213. 26. Fischer GH, Molenaar, I.W. Rasch Models Foundations, Recent Developments, and Applications. New York; 1995. 27. Mair P, Hatzinger, R. Extended Rasch modeling: The eRm package for the application of IRT models in R. Journal of Statistical Software 2007;20(9):1-20.
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439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478
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28. Hochberg Y, Benjamini Y. More powerful procedures for multiple significance testing. Statistics in medicine 1990;9(7):811-8. 29. WHO. Chapter 4: Health care and rehabilitation needs. WHO International Perspectives on Spinal Cord Injury. Geneva: World Health Organization 2013. p 67-91.
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30. Starrost K, Geyh S, Trautwein A, Grunow J, Ceballos-Baumann A, Prosiegel M et al. Interrater reliability of the extended ICF core set for stroke applied by physical therapists. Phys Ther 2008;88(7):841-51. 31. Wang W-C, Wilson M. The Rasch Testlet Model. Applied Psychological Measurement 2005;29(2):126-49. 32. Wilson M. Objective measurement: theory into practice. New Jersey: Norwood; 1994. 33. John EB, Liu W, Gregory RW. Biomechanics of muscular effort: age-related changes. Medicine and science in sports and exercise 2009;41(2):418-25. 34. Bergmark L, Westgren N, Asaba E. Returning to work after spinal cord injury: exploring young adults' early expectations and experience. Disability and rehabilitation 2011;33(2526):2553-8. 35. Hwang M, Zebracki K, Chlan KM, Vogel LC. Longitudinal employment outcomes in adults with pediatric-onset spinal cord injury. Spinal cord 2014. 36. Eriks-Hoogland IE, de Groot S, Post MW, van der Woude LH. Correlation of shoulder range of motion limitations at discharge with limitations in activities and participation one year later in persons with spinal cord injury. Journal of rehabilitation medicine : official journal of the UEMS European Board of Physical and Rehabilitation Medicine 2011;43(3):210-5. 37. Schilero GJ, Radulovic M, Wecht JM, Spungen AM, Bauman WA, Lesser M. A Center's Experience: Pulmonary Function in Spinal Cord Injury. Lung 2014. 38. Sale P, Mazzarella F, Pagliacci MC, Agosti M, Felzani G, Franceschini M. Predictors of changes in sentimental and sexual life after traumatic spinal cord injury. Archives of physical medicine and rehabilitation 2012;93(11):1944-9. 39. Valtonen K, Karlsson AK, Siosteen A, Dahlof LG, Viikari-Juntura E. Satisfaction with sexual life among persons with traumatic spinal cord injury and meningomyelocele. Disability and rehabilitation 2006;28(16):965-76. 40. Drake MJ, Cortina-Borja M, Savic G, Charlifue SW, Gardner BP. Prospective evaluation of urological effects of aging in chronic spinal cord injury by method of bladder management. Neurourology and urodynamics 2005;24(2):111-6. 41. Beuret-Blanquart F, Boucand MH. [Aging with spinal cord injury]. Annales de readaptation et de medecine physique : revue scientifique de la Societe francaise de reeducation fonctionnelle de readaptation et de medecine physique 2003;46(9):578-91. 42. Cieza A, Hilfiker R, Boonen A, van der Heijde D, Braun J, Stucki G. Towards an ICF-based clinical measure of functioning in people with ankylosing spondylitis: a methodological exploration. Disability and rehabilitation 2009;31(7):528-37. 43. WHO. Chapter 2: A global picture of spinal cord injury. WHO International Perspectives on Spinal Cord Injury. Geneva: World Health Organization2013. p 11-41.
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44. Post MW, Brinkhof MW, von Elm E, Boldt C, Brach M, Fekete C et al. Design of the Swiss Spinal Cord Injury Cohort Study. American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 2011;90(11 Suppl 2):S5-16.
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45. Stucki G, Kostanjsek N, Ustun B, Cieza A. ICF-based classification and measurement of functioning. European journal of physical and rehabilitation medicine 2008;44(3):315-28.
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534 535
RI PT
536 537 538 539
SC
540 541
M AN U
542 543 544 545 546
TE D
547
Table 1: Sociodemographic and injury related characteristics of the participants for the whole sample
549
and by resources of the country.
551 552 553 554 555 556 557 558 559 560 561
Figure 1: Person Item Map Body Functions and Body Structures
AC C
550
EP
548
Figure 2: Person Item Map Activity and Participation
Table 2: Rasch estimated difficulties, Standard Error (SE) and difficulty ranking for the ICF categories of the Body Functions and Body Structures (BF&BS) dimension, with indication of presence of misfit, Local Item Dependence (LID) and Differential Item Functioning (DIF). ICF categories from the Brief ICF Core Sets are marked with ‘c’, those from the statistical selection with ‘°’ and those which are a problem for more than 90% of the participants with ‘+’.
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Table 3: Rasch estimated difficulties, Standard Error (SE) and difficulty ranking for the ICF categories of the Activity and Participation (A&P) dimension, with indication of presence of misfit, Local Item Dependence (LID) and Differential Item Functioning (DIF). ICF categories from the Brief ICF Core Sets are marked with ‘c’, those from the statistical selection with ‘°’ and those which are a problem for more than 90% of the participants with ‘+’.
568
Figure 3: Local item dependences (LID) in the ICF categories in the Body function and Body Structure
569
(BF&BS) dimensions
RI PT
562 563 564 565 566 567
570
EP
TE D
M AN U
Figure 4: Local item dependences (LID) in the ICF categories in the Activity and Participation (A&P) dimensions
AC C
572 573 574
SC
571
ACCEPTED MANUSCRIPT
Age Years of formal education Situation (early post-acute)
187 158 208 332 87 300 408
TE D
208 58 62 46
12 39 220 106 37 16 38 Mean (SD ) 4.5 (6.8 )
EP
Time since injury
AC C
Injury Related
SCI level (tetraplegia) AIS impairment (complete) Bony vertebral injury (yes) Associated injury (yes) Spinal surgery (yes) Ventilatory assistance within last 24 hours (no) Asia Impairment Scale A B C D Injury Etiology Sports Assault Transportation Fall Other traumatic cause Non-traumatic spinal cord dysfunction Unspecified or unknown
44.0 37.2 55.6 78.9 20.8 70.8 99.0
RI PT
Socio-Demographic
Gender (male) Current marital status (married) Living alone (yes) Current occupation (Paid or Self-Employed)
M AN U
Characteristics
High Resource Countries Frequency % 623 59.4 484 77.7 278 45.0 160 25.8 256 41.1 Mean (SD ) 45 (15.8 ) 13.6 (3.9 ) Frequency %
SC
Low Resource Countries Frequency % 425 40.6 328 77.2 197 46.4 24 5.7 199 46.8 Mean (SD ) 37.9 (12.6 ) 9.7 (4.3 ) Frequency %
55.6 15.5 16.6 12.3
2.8 9.2 51.8 24.9 8.7 3.8 8.9
All Frequency 1048 812 475 184 455 Mean (SD ) 42.2 (15. ) 12.1 (4.5 ) Frequency
% 100 77.5 45.5 17.6 43.4
%
302 317 277 448 178 472 603
48.5 50.9 49.9 72.6 29.2 76.5 97.4
489 475 485 780 265 772 1011
46.7 45.3 52.2 75.1 25.8 74.2 98.1
277 60 106 112
49.9 10.8 19.1 20.2
485 118 168 158
52.2 12.7 18.1 17.0
68 29 214 117 78 112 88 Mean (SD ) 7.5 (11.4)
10.9 4.7 34.3 18.8 12.5 18.0 14.1
80 68 434 223 115 128 125 Mean (SD ) 6.2 (9.9)
7.6 6.5 41.4 21.3 11.0 12.2 11.9
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Differential Item Functioning (DIF)
Dimension: Body Functions and Body Structures (BF&BS )
o c o o o c o o c o o o c,o c,o o c,o o c,+ + + o o o c,o o c,o c,o o c,o
Infit MSQ
RI PT
c,o
0 1.74 1.08 2.27 -2.15 -2.19 2.64 1.24 3.27 2.04 0.58 0.33 -2.03 1.24 0.46 2.29 -2.37 -1.63 -1.36 -0.63 -0.11 -2.57 -3.23 -1.99 -1.55 -1.69 -1.96 0.67 -0.81 2.05 0.86 1.51 0.14
Outfit MSQ
1.49 1.35 1.15 1.37 0.79 0.73 0.93 0.87 1.25 0.77 0.73 0.76 0.74 0.96 0.87 0.98 0.86 1.02 1.18 0.85 1.04 0.68 1.08 0.82 0.97 1.07 0.72 1.16 1.08 0.89 0.93 1.05 1.80 1 3.03%
SC
o
Temperament and personality functions Energy and drive functions Sleep functions Emotional functions Sensory functions related to temperature and other stimuli Sensation of pain Blood vessel functions Blood pressure functions Haematological system functions Respiration functions Respiratory muscle functions Exercise tolerance functions Defecation functions Weight maintenance functions Thermoregulatory functions Urinary excretory functions Urination functions Sexual functions Sensations associated with genital and reproductive functions Mobility of joint functions Stability of joint functions Muscle tone functions Muscle endurance functions Motor reflex functions Involuntary movement reaction functions Control of voluntary movement functions Sensations related to muscles and movement functions Protective functions of the skin Sensation related to the skin Structure of respiratory system Structure or urinary system Structure of shoulder region Structure of areas of skin Number of significant ICF-categories Percentage of significant ICF-categories
Rank SE1 Item Difficulty2 Difficulty 0 16 0.08 27 0.07 23 0.09 30 0.1 5 0.1 4 0.1 32 0.08 24 0.13 33 0.09 28 0.07 20 0.07 18 0.1 6 0.08 24 0.07 19 0.09 31 0.11 3 0.09 10 0.08 12 0.07 14 0.07 15 0.11 2 0.14 1 0.09 7 0.08 11 0.09 9 0.09 8 0.07 21 0.07 13 0.09 29 0.07 22 0.08 26 0.07 17
M AN U
o
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o
EP
b126 b130 b134 b152 b270 b280 b415 b420 b430 b440 b445 b455 b525 b530 b550 b610 b620 b640 b670 b710 b715 b735 b740 b750 b755 b760 b780 b810 b840 s430 s610 s720 s810
Title
AC C
ICF-code
Item Difficulty
1.20 1.13 1.08 1.17 0.81 0.84 0.90 0.84 0.97 0.84 0.80 0.84 0.93 0.98 0.89 1.03 0.97 0.96 1.02 0.94 1.01 0.88 0.99 0.86 0.97 1.04 0.86 1.13 1.03 0.85 0.93 0.86 1.13 0
LID
Gender
Age
X X X X X
X X X
X
X X X X
X X
X X X X
X
X X X X X 17 51.52%
4 12.12%
4 12.12%
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TE D
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SE = Standard Error Increasing rank, decreasing probability for a problem
EP
2
AC C
1
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Differential Item Functioning (DIF)
Dimension: Activity and Participation (A&P )
0.99 1.09 1.73 0.75 0.78 0.64 0.99 0.89 1.13 1.37 0.72 1.11 1.10 1.08 0.52 0.55 0.60 0.65 0.65 0.62 0.68 1.04 0.74 0.99 1.43 2.06 1.24 1.46 1.26 1.25 1.97
Infit MSQ
LID 0.98 1.06 1.18 0.87 0.87 0.76 1.00 0.89 1.10 1.05 0.95 1.03 1.08 1.08 0.68 0.70 0.74 0.75 0.78 0.77 0.82 1.04 0.88 1.06 1.22 1.07 1.14 1.17 1.17 1.06 1.17
3 9.68%
Gender
0
Age
RI PT
16 25 29 27 6 5 1 18 4 2 3 10 9 14 11 12 7 8 23 26 19 17 13 15 24 31 28 21 22 20 30
Outfit MSQ
X
SC
0 1.28 1.75 1.69 -1.29 -1.34 -3.39 0.48 -2.87 -3.31 -3.1 -1.01 -1.02 -0.35 -0.81 -0.55 -1.07 -1.04 1.1 1.32 0.59 0.05 -0.55 -0.19 1.28 3.06 1.72 0.84 0.9 0.61 2.39
Rank Difficulty2
M AN U
c
SE1 Item Difficulty 0.00 0.08 0.08 0.08 0.09 0.09 0.14 0.07 0.12 0.14 0.13 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.07 0.08 0.07 0.07 0.08 0.08 0.08 0.11 0.08 0.07 0.07 0.07 0.09
TE D
o
Acquiring skills Carrying out daily routine c,o Handling stress and other psychological demands o Using communication devices and techniques c Changing basic body position c Transferring oneself + Moving objects with lower extremities c,o Hand and arm use c Walking c,+ Moving around + Moving around in different locations c,o Moving around using equipment c Using transportation o Driving c Washing oneself c,o Caring for body parts c,o Toileting c Dressing c Eating c Drinking o Looking after one's health o Acquisition of goods and services o Preparing meals o Assisting others o Intimate relationships o School education o Apprenticeship (work preparation) o Acquiring, keeping and terminating a job o Economic self-sufficiency o Community life o Religion and spirituality Number of significant ICF-categories Percentage of significant ICF-categories 1 SE = Standard Error 2 Increasing rank, decreasing probability for a problem d155 d230 d240 d360 d410 d420 d435 d445 d450 d455 d460 d465 d470 d475 d510 d520 d530 d540 d550 d560 d570 d620 d630 d660 d770 d820 d840 d845 d870 d910 d930
Item Difficulty
EP
Title
AC C
ICF-code
X X X X
X
X X X X X X
X
X X
X X
X X
X
15 48.39%
0 0.00%
5 16.13%
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Person Parameter Distribution
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● ● ● ● ● ● ● ● ● ● ●
ttx
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TE D
M AN U
SC
b740 Muscle endurance functions b735 Muscle tone functions b620 Urination functions b280 Sensation of pain b270 Sensory functions related to temperature and other stimuli b525 Defecation functions b750 Motor reflex functions b780 Sensations related to muscles and movement functions b760 Control of voluntary movement functions b640 Sexual functions b755 Involuntary movement reaction functions b670 Sensations associated with genital and reproductive functions b840 Sensation related to the skin b710 Mobility of joint functions b715 Stability of joint functions s810 Structure of areas of skin b455 Exercise tolerance functions b550 Thermoregulatory functions b445 Respiratory muscle functions b810 Protective functions of the skin s610 Structure or urinary system b134 Sleep functions b420 Blood pressure functions b530 Weigth maintenance functions s720 Structure of shoulder region b130 Energy and drive functions b126 Temperament and personality functions b440 Respiration functions s430 Structure of respiratory system b152 Emotional functions b610 Urinary excretory functions b415 Blood vessel functions b430 Haematological system functions
RI PT
Person Item Map
AC C
EP
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
−5
−4
−3
−2
−1
0
1
Functioning
2
3
4
5
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Person Item Map
● ● ●
d435 Moving objects with lower extremities d455 Moving around d460 Moving around in different locations d450 Walking d420 Transferring oneself d410 Changing basic body position d530 Toileting d540 Dressing d470 Using transportation d465 Moving around using equipment d510 Washing oneself d520 Caring for body parts d630 Preparing meals d475 Driving d660 Assisting others d620 Acquisition of goods and services d445 Hand and arm use d570 Looking after one's health d910 Community life d845 Acquiring, keeping and terminating a job d870 Economic self−sufficiency d550 Eating d770 Intimate relationships d230 Carrying out daily routine d560 Drinking d360 Using communication devices and techniques d840 Apprenticeship (work preparation) d240 Handling stress and other psychological demands d930 Religion and spirituality d155 Acquiring skills d820 School education
● ● ● ● ● ● ●
ttx
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Person Parameter Distribution
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EP
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AC C
● ● ● ● ● ● ● ● ● ● ● ●
−5
−4
−3
−2
−1
0
Functioning
1
2
3
4
AC C
EP
TE D
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