Acta Clinica Belgica International Journal of Clinical and Laboratory Medicine
ISSN: 1784-3286 (Print) 2295-3337 (Online) Journal homepage: http://www.tandfonline.com/loi/yacb20
Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire A. C. Rohenkohl, J. De Schepper, J. Vanderfaeillie, K. Fricke, S. Hendrickx, K. Lagrou, M. Bullinger & J. Quitmannthe QoLISSY Study Group To cite this article: A. C. Rohenkohl, J. De Schepper, J. Vanderfaeillie, K. Fricke, S. Hendrickx, K. Lagrou, M. Bullinger & J. Quitmannthe QoLISSY Study Group (2014) Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire, Acta Clinica Belgica, 69:3, 177-182, DOI: 10.1179/2295333714Y.0000000024 To link to this article: http://dx.doi.org/10.1179/2295333714Y.0000000024
Published online: 02 Apr 2014.
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Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire A. C. Rohenkohl1, J. De Schepper2,3, J. Vanderfaeillie4, K. Fricke1, S. Hendrickx4, K. Lagrou3, M. Bullinger1, J. Quitmann1, the QoLISSY Study Group University Hospital Center Hamburg–Eppendorf; Department of Medical Psychology, Germany, 2Universitair Ziekenhuis Brussel, Division of Pediatric Endocrinology, Belgium, 3Universitair Ziekenhuis Gent; Division of Pediatric Endocrinology, Belgium, 4Vrije Universiteit Brussel, Department of Clinical and Lifespan Psychology, Belgium
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Objectives: The Quality of Life in Short Stature Youth (QoLISSY) questionnaire was recently developed in five European countries to assess health-related quality of life in children and adolescents with idiopathic short stature or growth hormone deficiency from child and parent perspectives. In addition to the existing French version, a Flemish version is needed for use of QoLISSY in the Flemish speaking part of Belgium. Methods: Children (8–18 years) and their parents recruited from two Belgian paediatric endocrinology clinics completed the QoLISSY in a cross-sectional study. Cronbach’s Alpha and test–retest reliability was assessed. Validity was examined by correlation with the generic KIDSCREEN questionnaire as well as by group comparisons according to diagnostic and treatment status. Results: The QoLISSY scales had an acceptable internal consistency with Cronbach’s Alpha ranging from 0.80 to 0.94 (child version) and from 0.77 to 0.92 (parent version). Test–retest reliability correlation coefficients ranged from r50.75 to 0.89 in the child version and from r50.58 to 0.85 in the parent version. Moderate correlations with the generic KIDSCREEN questionnaire suggested construct validity. Differences between child groups according to child age, underlying diagnosis, and degree of height deficit were found. Correlations with the European QoLISSY were significant for all scales. Discussion: The Flemish QoLISSY instrument is a psychometrically sound, reliable, and valid short stature specific questionnaire measuring health-related quality of life. It is expected to be of great use in upcoming clinical research on growth disorders and growth hormone treatment in Belgium and Europe. Keywords: Children, Psychometric properties, Quality of life, Questionnaire development, Short stature
Introduction In paediatric endocrinology, child reported outcomes are needed to measure benefits of treatment regarding health-related quality of life (HrQoL) describing the subjective aspects of physical, emotional, and social well-being and functioning from the perspective of the young children and their parents.1–4 However, only few condition-specific instruments are currently available for assessing the HrQoL in children and adolescents seeking treatment for their short stature.5 Recently, a condition-specific quality of life (QoL) questionnaire was developed by the European QoLISSY (Quality of Life in Short Stature Youth) Study Group, consisting of 50 items for the child version for children and adolescents and 66 items for Correspondence to: A. C. Rohenkohl, University Hospital Center Hamburg–Eppendorf, Department of Medical Psychology, Martinistrasse 52, W26, 20246 Hamburg, Germany. Email: [email protected]
ß Acta Clinica Belgica 2014 DOI 10.1179/2295333714Y.0000000024
the parent version.6 The QoLISSY instrument is the result of a simultaneous cross cultural development process involving children with either treated or untreated growth hormone deficiency (GHD) or idiopathic short stature (ISS) in five European countries (UK, Spain, France, Sweden, and Germany).7 In contrast to other European countries, GH therapy in Belgium is made available for children with idiopathic short stature by a company driven medical need program, making it an equally frequent condition as GHD to start GH treatment in clinical practice. To assess the experience of short stature and the benefits of treatment, measurement of child and parent reported QoL outcomes is necessary. In order to use the existing European QoLISSY questionnaire for clinical and research purpose in Flemish speaking children and their parents in
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Belgium, the translation, cultural adaptation, and validation of the English version of the QoLISSY instrument was undertaken.8 The applicability of the developed Flemish version in terms of the different topics and statements as well as in terms of statistical comparison of psychometric indicators was investigated. In this study, the psychometric properties of the Flemish version of the QoLISSY instrument, including internal consistency and test–retest reliability, convergent and discriminant validity, as well as concordance between the Flemish and European dataset are reported.
Materials and Methods Study sample
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Children with short stature (stature below –2 SDS9) aged between 8 and 18 years as well as their parents were recruited from the divisions of paediatric endocrinology of the University Hospitals of Brussels and Gent by telephone contact. In addition, parents of younger children aged between 4 and 7 years participated. All children were diagnosed either with ISS or GHD and had a height (22 SDS at date of diagnosis. Children with multiple pituitary hormone deficiency and/or severe mental conditions were excluded. Efforts were made to include both GH-treated and -untreated children with an equal distribution of gender and age groups (4–7, 8–12, and 13–18 years). All parents signed an informed consent form before participation; children from the age of 13 years gave assent. The study was approved by the appropriate ethics committees and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
Study design For the cultural adaptation, the questionnaire was translated from of the original English QoLISSY version into Flemish by a Flemish speaking psychologist. A back translation was provided by a second Flemish speaker. Independent native speakers reviewed the Flemish forward and backward translation and provided the pilot test version. The study design involved two phases: a focus group and cognitive debriefing phase with a pilot test and a field test with re-test phase. Within the focus groups/ cognitive debriefing in Belgium 18 children/adolescents and 26 parents discussed the pilot version.6 The focus group discussions were performed in cooperation with psychologists of the Department of Psychology and Educational Sciences of the Vrije Universiteit Brussel and of the Department of Endocrinology of the University Hospital of Gent. Age-specific child (8–12, 13–18 years) and parent (4– 7, 8–12, 13–18 years) focus group discussions were
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carried out together with a cognitive debriefing and pilot testing of the Flemish translated questionnaires (child and parent version). The most important aspects of quality of life of children with short stature were discussed during the first part of the focus groups. During the second part, children (8–18 years) and parents completed the QoLISSY instrument separately (pilot test) followed by a cognitive debriefing session. Each participant was asked to comment on their personal perceptions of the questions and their level of understanding. In addition, they were asked to evaluate the sensitivity, importance, clarity, and relevance of each item as it relates to their (or their child’s) height. No additional concepts or domains associated with QoL for both child and adolescent age group were identified in the focus groups and no further issues were identified by the cognitive debriefing panel. Since neither needs for adaptation nor for modifications in wording had been encountered, the pooled data from the pilot and the field test procedures were used in the validation analysis. For the field test, 18 additional children (8– 12 years; 13–18 years) and 27 parents (4–7 years; 8– 12 years; 13–18 years) were contacted via mail. The retest was distributed per mail with the request of completion within ten days (N523 children/adolescents and 32 parents).
Questionnaire scoring Based on the European QoLISSY Manual, the QoLISSY-QoL total score is calculated as mean of the core module.6 The 22 items QoLISSY-QoL core module includes three scales: Physical QoL (6 items), Social QoL (8 items) and Emotional QoL (8 items). Furthermore, three additional scales cover Treatment specific aspects (only for treated children; 14 items), aspects of Coping (10 items) and general Beliefs about height (5 items) as determinants of QoL. Two additional scales of the parent version contain questions about the child’s Future (4 items) and Effects of short stature on parents (11 items). A fivepoint Likert scale was used as a response scale ranging from 0 (‘not at all/never’) to 5 (‘extremely/ always’). Mean scores of each scale were calculated and transformed into values between 0 and 100, while higher values indicate a higher QoL. For validation purposes, children aged between 8 and 18 years also completed the KIDSCREEN 52 questionnaire, a wellvalidated and widely distributed generic HrQoL instrument.10 The KIDSCREEN 52 covers 10 domains: Physical Well-being (5 items), Psychological Well-being (6 items), Moods & Emotions (7 items), SelfPerception (5 items), Autonomy (5 items), Parent Relations & Home Life (6 items), Social Support &
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Peers (6 items), School Environment (6 Items), Social Acceptance (Bullying) (3 items), and Financial Resources (3 items). Socio-demographic data (e.g. gender and age) as well as clinical data (e.g. diagnosis, treatment status, duration of treatment, age at start of treatment) were gathered from child medical files. Height standard deviations scores were calculated using recent Flemish growth references.11
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Data analysis Scale characteristics such as mean (M) and standard deviation (SD) were examined together with floor and ceiling effects (percentage of responses at the lowest and highest scale end to describe the distribution or respondent responses in this sample). Cronbach’s Alpha was calculated for each domain and for the total score as an index of internal consistency. Test– retest reliability was assessed by calculation of the correlations for each time point for each domain and the total score for both the parents’ and the child’s version, using the Pearson’s correlation analysis. Convergent validity was assessed using the correlations between the QoLISSY and the KIDSCREEN 52 in the field test sample. Since the latter questionnaire was only distributed in the child version, correlations were only analysed between the QoLISSY child version and the KIDSCREEN 52 child version. Pearson’s correlations between QoLISSY scale scores of children and parents as well as the intraclass correlation coefficient between child and parent scores were calculated to examine concordance of ratings. The mean scale values of the Flemish sample were compared with the European sample using ttests (normal distribution was tested). In addition, correlations were calculated and compared using a Fisher z-transformation. Differences between gender (boy/girl) and age-group (4–7, 8–12, 13–18 years) as well as group differences according to diagnosis (ISS/ GHD), treatment status (treated/untreated), and degree of short stature ((22 SD, .2 SD) were analysed by non-parametric tests (Kruskal–Wallis test/Mann–Whitney U test). All statistical calculations were performed using the SPSS 18.0 software.11
Results Demographic characteristics From 56 families (one child and one parent) having agreed to participate in the field test, 54 families returned the questionnaires (4% drop-out). One questionnaire was excluded because of incompleteness. As a consequence, analyses are based on a total of 53 questionnaire sets: 36 parent’s and child’s versions from children aged more than 7 years and 17 parent’s versions of children aged between 4 and 7 years. Table 1 summarizes the demographic characteristics of the included children. Thirty-six boys
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Table 1 Demographic characteristics of the participating families (total sample) 4–7 years* 8–12 years 13–18 years Total n Gender Girl 7 Boy 10 Diagnosis GHD 5 ISS 12 Treatment status Untreated 10 GH-treated 7 Height SD (22 SDS 12 .22 SDS 5
%
n
%
n
%
n %
41.2 58.8
3 8
27.3 72.7
7 18
28.0 72.0
1732.1 3667.9
29.4 70.6
2 9
18.2 81.8
5 20
20.0 80.0
1222.6 4177.4
58.8 41.2
3 8
27.3 72.7
10 15
40.0 60.0
2343.4 3056.6
70.6 29.4
6 5
54.5 45.5
21 4
84.0 16.0
3973.6 1426.4
Note: *Only parents participated in the child’s age group 4– 7 years.
and 17 girls were included with more boys than girls in all age groups. Seventeen children were aged between 4 and 7 years, 11 between 8 and 12 years, and 25 between 13 and 18 years. Overall, 12 children were diagnosed with GHD and 41 with ISS. The distribution of treatment status was almost even (n untreated523 and n treated530). Although all children did meet the inclusion criteria at the time of diagnosis, 14 children were presently taller than 22 SD, while 39 children had a height SD below (22 SD at the time of analysis.
Reliability testing The scale means (M; on a scale 0–100 with 100 reflecting highest quality of life) ranged from 49.27 (Treatment) to 73.04 (Physical QoL) in the child’s version and from 46.68 (Coping) to 80.20 (Future) in the parent version. Overall mean scores identify a high level of subjective quality of life in young respondents, reaching about 73–80% of the scale with high standard deviations (SD) indicating substantive variance within the scales. Low floor (2.9–4.8% for children; 1.9–7.1% for parents) and low to moderate ceiling effects (2.9–22.9% for children; 2.0–22.4% for parents), as well as high reliabilities were observed for the overall data set. Cronbach‘s Alpha ranged from alpha50.80 (Physical QoL) to alpha50.94 (QoL total Score) for the child‘s version and from alpha50.77 (Physical QoL) to alpha50.92 (QoL total Score) for the parent’s version. The test–retest reliability was examined in 32 cases (60.4%) with completed retest questionnaires. Pearson correlation coefficients ranged from r50.75 (Physical QoL) to 0.89 (QoL total Score) in the child version and from r50.58 (Coping) to 0.85 (QoL total Score/Treatment/Emotional QoL) in the parent version.
Group comparison Neither the parent’s nor the child’s version revealed any significant gender differences, whereas significant
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differences were found between age groups: mean scores on the Beliefs scale were lower for older (M567.75; SD518.82) children compared to younger children (M586.25; SD518.82) in the child version (U(33)55.06; P50.024). In the parent’s version, scores were lower for older children (M585.91; SD516.40) on the Future scale as compared to younger children (M592.14; SD57.77) (H(2)510.38; P50.006).
Convergent validity testing
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Pearson’s correlation coefficients between QoLISSY and KIDSCREEN 52 were moderate to high between Social Acceptance (Bullying) and Social/Emotional in the QoLISSY child version (r50.54 and r50.48, see Table 4). Children with high scores on the QoLISSY coping module reported to get along well with their peers (Social Support & Peers r50.57) and did not perceive themselves as physically restricted (Physical Well-being r50.57). A high score on the QoLISSY Physical scale was also related to a high score on Autonomy and Self-Perception in the KIDSCREEN. The Self-Perception scale correlated with several QoLISSY scales. On the other hand, the correlations between the physical scales as well as the social scales of the two questionnaires were non-significant (Table 2).
Known groups differences Only the mean of the Coping scale in the child‘s questionnaire differed significantly between the two diagnostic groups: children with GHD scored lower on the Coping scale than children diagnosed with ISS (U(31)536.50; P50.045). On all other scales, children with GHD and ISS had similar results. When comparing untreated with GH treated children, no significant differences in any of the QoLISSY scales were found in both the parent’s and child’s versions. Regarding the degree of short stature, differences were found for the scales Physical QoL (PChildren50.004 and PParents50.004), Social QoL (PChildren50.008 and PParents50.017), Emotional QoL (PChildren50.015), Beliefs (PChildren50.002), Future (PParents50.032),
Effects on Parents (PParents50.047), and in the total QoL score (PChildren50.011 and PParents50.027), indicating that perceived QoL was higher for the less short children.
Child–parent concordance The parent’s version correlated significantly with the child’s version on all scales across families, with Pearson’s correlation (r) ranging from 0.48 (Physical) to 0.74 (Treatment). Within child parent pairs the intraclass correlation coefficient shows nearly the same results and ranges from r50.46 (Physical QoL) to 0.74 (Treatment).
Comparison with the international sample When comparing the Flemish sample (n553) with the original European sample (n5303), more ISS patients were included in Belgium (77.4%) than in the international sample (59.3%). In addition, more adolescents between 13 and 18 years were included in Belgium (69.4%) as compared to the international sample (51%). Treated and untreated children were equally represented in the samples. While in the international sample, the distribution across the height groups was comparable, more short children ((22 SDS) were included in the Belgian sample (73.6%). Nevertheless only the Effects on Parents scale in the parent’s version differed significantly between samples (t(75)52.87, P50.005), indicating a higher QoL for the Flemish sample (M571.29; SD520.06) concerning the Effects on Parents as compared to the international sample (M562.23; SD524.77). The comparison of Cronbach’s Alpha shows slightly higher values for internal consistency in the Flemish sample with alpha.0.80 for the scales of the QoLISSY core module as compared to the European sample (alpha.0.70). Examining the concordance between QoLISSY subscales by inter-scale correlations, the child’s versions showed significant correlations with similar correlation coefficients. Only two correlations that were significant in the European sample were not statistically significant in the Flemish sample (Treatment/Coping and Treatment/Beliefs). However,
Table 2 Correlation of the QoLISSY with the KIDSCREEN 52 (patient-report) scales Physical Social Emotional Coping Beliefs Treatment QoL total score KIDSCREEN 52 Physical well-being Psychological well-being Moods and emotions Self-perception Autonomy Parent relations and home life Financial resources Social support and peers School environment Social acceptance (bullying) Note: *P,0.05, **P,0.01.
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0.22 0.32 0.35 0.56** 0.47** .08 0.21 0.07 0.27 0.43*
0.37* 0.36* 0.37* 0.64** 0.22 0.09 0.42* 0.30 0.16 0.54**
0.26 0.39* 0.44* 0.68** 0.31 0.10 0.37* 0.30 0.33 0.48**
0.57** 0.45* 0.18 0.43* 0.27 0.27 0.17 0.57** 0.17 0.36*
.10 0.30 0.26 0.53** 0.38* 0.12 0.24 0.04 0.40* 0.15
0.24 0.06 20.17 0.07 0.22 0.08 20.11 0.22 20.16 20.07
0.29 0.41* 0.41* 0.67** 0.35* 0.11 0.36* 0.24 0.30 0.53*
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the correlation coefficients were similar (r50.23 versus r50.26 and r520.12 versus r520.18). The parent’s versions showed similar correlation coefficients as well. Compared to the European version, three correlations were not significant in the Flemish sample: between Physical and Treatment, Social and Treatment and the total score and Treatment. These correlation coefficients were small ranging from r50.21 to 0.25. The other correlation coefficients were similar and had the same direction (Table 3).
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Discussion Although a rather small convenience sample was used for the cultural adoption of the QoLISSY instrument for Flemish speaking children in Belgium, it was done by a sophisticated content-valid and robust procedure, as defined by the European QoLISSY Study Group.6 The validity of the multi-language QoLISSY instrument was previously confirmed by a satisfactory content, criterion, as well as construct validity in 268 children and 317 parents.6,7 The results of the pilot and field tests in 53 children and/or parents did provide an insight into important psychometric properties of the Flemish QoLISSY version, namely, reliability and validity. The internal consistencies were overall satisfactory with Cronbach’s alpha.0.70. The test–retest reliability was also acceptable with r values ranging from 0.75 to 0.89 in the child’s version and from 0.58 to 0.85 in the parent’s version. Overall, the Flemish version of the QoLISSY questionnaire can thus be considered a reliable instrument. Furthermore, the positive and statistically significant correlations between the QoLISSY and the KIDSCREEN 52 are an indication of its convergent validity. Moreover, high correlations were found between all QoLISSY scales and the KIDSCREEN Self-Perception domain, indicating that aspects measured by the QoLISSY reflect issues of selfperception. It must be stressed that physical items in QoLISSY questionnaire are height-related and thus, evaluate different aspects of physical well-being as compared to the KIDSCREEN scale. In contrast to the observed group validity in the European sample for the degree of shortness, treatment status, and diagnostic criteria, only a small impact of shortness was observed in the Flemish sample. This might be
QoLISSY Flemish version
related to the rather small sample size. On the other hand, children with ISS were overrepresented in our sample, in contrast to the European sample. The concordance between parent and child versions of the impact of short stature was reasonably high with few exceptions. However, as recommended by Matza et al.,8 the use of parental report of the child’s quality of life should be used with caution when self-report is unavailable (e.g. age) or the concept of interest is not directly observable (e.g. pain and emotional issues). In the case of the QoLISSY, the parent specific mediator domain of Effect on Parents provides a perspective not normally considered in measures of outcome in children. The authors recommend that the QoLISSY parent version can be used to supplement the information obtained directly from the child rather than to substitute for the child when measuring the child is possible. In spite of slight differences in the composition of samples, the distribution of scale scores within the Flemish and the original European QoLISSY instrument was comparable. Except for the Effects on Parents scale, agreement between the Flemish and the original European psychometric properties of the questionnaire was high. The inter-scale correlations were similar for the Flemish and the European questionnaire, suggesting comparable patterns of scale relationship. The small sample size and the cross-sectional design is a weakness of the Flemish validation study. In order to confirm the factorial validity with a confirmatory factor analysis, studies with larger samples including more families with short statured children (ISS/GHD) are needed. Nevertheless, the psychometric analyses of the Flemish QoLISSY field test yielded promising results. The Flemish QoLISSY version appears to be a reliable and valid instrument to assess QoL in children and adolescents referred to growth clinics for short stature due to idiopathic short stature or growth hormone deficiency and can be used in studies across Europe, including Belgium. The instrument is currently tested in a Dutch speaking sample of short statured children and adolescents in the Netherlands so that psychometric results can be compared within one language and across two countries.
Table 3 Inter-scale correlations between the Flemish and European sample (patient/parent-report) Scale
Physical
Social
Emotional
Coping
Beliefs
Treatment
QoL total score
Physical Social Emotional Coping Beliefs Treatment QoL total score
… 0.73**/0.78** 0.70**/0.63** 0.04/20.05 0.68**/0.58** 0.11/0.11 0.87**/0.90**
… 0.90**/0.78** 0.35/20.03 0.58**/0.56** 0.19/0.03 0.96**/0.95**
… 0.30/20.05 0.70**/0.54** 0.08/20.02 0.94**/0.86**
… 0.04/0.02 0.23/0.26** 0.23/20.05
… 20.12/20.18* 0.71**/0.62**
… 0.11/0.05
…
Note: *P,0.05, **P,0.01.
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Conflict of Interest
References
The project was funded by Pfizer and the authors were provided funding for its conduct at each site. There are no additional competing interests to report.
1 Bullinger M, Schmidt S, Petersen C, Erhart M, Ravens-Sieberer U. [Methodological challenges and potentials of health-related quality of life evaluation in children with chronic health conditions under medical health care]. Med Klin. 2007;102:734–45. German. 2 Bullinger M. Psychological criteria for treating children with idiopathic short stature. Horm Res Paediatr. 2011;76:20–3. 3 Chaplin JE. Growth-related quality of life. Horm Res Paediatr. 2011;76:51–2. 4 Noeker M. Psychological functioning in idiopathic short stature. Horm Res Paediatr. 2011;76:52–6. 5 Bru¨tt AL, Sandberg DE, Chaplin J, Wollmann H, Noeker M, Kołtowska-Ha¨ggstro¨m M, et al. Assessment of health-related quality of life and patient satisfaction in children and adolescents with growth hormone deficiency or idiopathic short stature — part 1: a critical evaluation of available tools. Horm Res. 2009;72:65–73. 6 The European QoLISSY Group. Quality of life in short stature youth. The QoLISSY questionnaire – user’s manual. Lengerich: Pabst Science Publishers; 2013. 7 Bullinger M, Quitmann J, Power M, Herdman M, Mimoun E, DeBusk K, et al. Assessing the quality of life of health-referred children and adolescents with short stature: development and psychometric testing of the QoLISSY instrument. Health Qual Life Outcomes. 2013;11:76. 8 Matza LS, Patrick DL, Riley AW, Alexander JJ, Rajmil L, Pleil AM, et al. Pediatric patient-reported outcome instruments for research to support medical product labeling: report of the ISPOR PRO Good Research Practices for the Assessment of Children and Adolescents Task Force. Value Health. 2013;16:461–79. 9 Kant SG, Wit JM, Breuning MH. Genetic analysis of short stature. Horm Res. 2003;60:157–65. 10 The KIDSCREEN Group Europe. The KIDSCREEN questionnaires: quality of life for children and adolescents — handbook. Lengerich: Pabst Science Publishers; 2006. 11 SPSS Inc. PASW for Windows, Version 18.0. Chicago, IL: SPSS Inc.; 2009.
Acknowledgements
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QoLISSY is a joint initiative between Pfizer and the University Medical Centre Hamburg–Eppendorf. Copyright Pfizer all rights reserved. The QoLISSY instrument, together with comprehensive information of its development and validation process, is published in the QoLISSY’s User’s Manual (Lengerich: Pabst Science Publishers; 2013). The QoLISSY study group, in addition to the German team of Monika Bullinger and Julia Quitmann (University Medical Centre Hamburg-Eppendorf, Department of Medical Psychology, Hamburg, Germany), includes John E. Chaplin (Sahlgrenska Academy at University of Gothenburg, Department of Paediatrics, Va¨xthuset, Queen Silvia’s Children’s Hospital, Gothenburg, Sweden), Michael Herdman (IMIM University, Insight Consulting and Research, Barcelona, Spain), Emmanuelle Mimoun (University of Toulouse, Department of Pediatric Endocrinology, Toulouse, France), Andreas Pleil (Pfizer, Inc. Specialty Care MDG, Outcomes Research, San Diego, CA), Hartmut Wollmann (University of Tuebingen), and Michael Power (University of Edinburgh, Department of Clinical Psychology, Edinburgh, Scotland).
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ISSN: 1784-3286 (Print) 2295-3337 (Online) Journal homepage: http://www.tandfonline.com/loi/yacb20
Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire A. C. Rohenkohl, J. De Schepper, J. Vanderfaeillie, K. Fricke, S. Hendrickx, K. Lagrou, M. Bullinger & J. Quitmannthe QoLISSY Study Group To cite this article: A. C. Rohenkohl, J. De Schepper, J. Vanderfaeillie, K. Fricke, S. Hendrickx, K. Lagrou, M. Bullinger & J. Quitmannthe QoLISSY Study Group (2014) Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire, Acta Clinica Belgica, 69:3, 177-182, DOI: 10.1179/2295333714Y.0000000024 To link to this article: http://dx.doi.org/10.1179/2295333714Y.0000000024
Published online: 02 Apr 2014.
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Date: 01 April 2016, At: 12:43
Validation of the Flemish version of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire A. C. Rohenkohl1, J. De Schepper2,3, J. Vanderfaeillie4, K. Fricke1, S. Hendrickx4, K. Lagrou3, M. Bullinger1, J. Quitmann1, the QoLISSY Study Group University Hospital Center Hamburg–Eppendorf; Department of Medical Psychology, Germany, 2Universitair Ziekenhuis Brussel, Division of Pediatric Endocrinology, Belgium, 3Universitair Ziekenhuis Gent; Division of Pediatric Endocrinology, Belgium, 4Vrije Universiteit Brussel, Department of Clinical and Lifespan Psychology, Belgium
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Objectives: The Quality of Life in Short Stature Youth (QoLISSY) questionnaire was recently developed in five European countries to assess health-related quality of life in children and adolescents with idiopathic short stature or growth hormone deficiency from child and parent perspectives. In addition to the existing French version, a Flemish version is needed for use of QoLISSY in the Flemish speaking part of Belgium. Methods: Children (8–18 years) and their parents recruited from two Belgian paediatric endocrinology clinics completed the QoLISSY in a cross-sectional study. Cronbach’s Alpha and test–retest reliability was assessed. Validity was examined by correlation with the generic KIDSCREEN questionnaire as well as by group comparisons according to diagnostic and treatment status. Results: The QoLISSY scales had an acceptable internal consistency with Cronbach’s Alpha ranging from 0.80 to 0.94 (child version) and from 0.77 to 0.92 (parent version). Test–retest reliability correlation coefficients ranged from r50.75 to 0.89 in the child version and from r50.58 to 0.85 in the parent version. Moderate correlations with the generic KIDSCREEN questionnaire suggested construct validity. Differences between child groups according to child age, underlying diagnosis, and degree of height deficit were found. Correlations with the European QoLISSY were significant for all scales. Discussion: The Flemish QoLISSY instrument is a psychometrically sound, reliable, and valid short stature specific questionnaire measuring health-related quality of life. It is expected to be of great use in upcoming clinical research on growth disorders and growth hormone treatment in Belgium and Europe. Keywords: Children, Psychometric properties, Quality of life, Questionnaire development, Short stature
Introduction In paediatric endocrinology, child reported outcomes are needed to measure benefits of treatment regarding health-related quality of life (HrQoL) describing the subjective aspects of physical, emotional, and social well-being and functioning from the perspective of the young children and their parents.1–4 However, only few condition-specific instruments are currently available for assessing the HrQoL in children and adolescents seeking treatment for their short stature.5 Recently, a condition-specific quality of life (QoL) questionnaire was developed by the European QoLISSY (Quality of Life in Short Stature Youth) Study Group, consisting of 50 items for the child version for children and adolescents and 66 items for Correspondence to: A. C. Rohenkohl, University Hospital Center Hamburg–Eppendorf, Department of Medical Psychology, Martinistrasse 52, W26, 20246 Hamburg, Germany. Email: [email protected]
ß Acta Clinica Belgica 2014 DOI 10.1179/2295333714Y.0000000024
the parent version.6 The QoLISSY instrument is the result of a simultaneous cross cultural development process involving children with either treated or untreated growth hormone deficiency (GHD) or idiopathic short stature (ISS) in five European countries (UK, Spain, France, Sweden, and Germany).7 In contrast to other European countries, GH therapy in Belgium is made available for children with idiopathic short stature by a company driven medical need program, making it an equally frequent condition as GHD to start GH treatment in clinical practice. To assess the experience of short stature and the benefits of treatment, measurement of child and parent reported QoL outcomes is necessary. In order to use the existing European QoLISSY questionnaire for clinical and research purpose in Flemish speaking children and their parents in
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Belgium, the translation, cultural adaptation, and validation of the English version of the QoLISSY instrument was undertaken.8 The applicability of the developed Flemish version in terms of the different topics and statements as well as in terms of statistical comparison of psychometric indicators was investigated. In this study, the psychometric properties of the Flemish version of the QoLISSY instrument, including internal consistency and test–retest reliability, convergent and discriminant validity, as well as concordance between the Flemish and European dataset are reported.
Materials and Methods Study sample
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Children with short stature (stature below –2 SDS9) aged between 8 and 18 years as well as their parents were recruited from the divisions of paediatric endocrinology of the University Hospitals of Brussels and Gent by telephone contact. In addition, parents of younger children aged between 4 and 7 years participated. All children were diagnosed either with ISS or GHD and had a height (22 SDS at date of diagnosis. Children with multiple pituitary hormone deficiency and/or severe mental conditions were excluded. Efforts were made to include both GH-treated and -untreated children with an equal distribution of gender and age groups (4–7, 8–12, and 13–18 years). All parents signed an informed consent form before participation; children from the age of 13 years gave assent. The study was approved by the appropriate ethics committees and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
Study design For the cultural adaptation, the questionnaire was translated from of the original English QoLISSY version into Flemish by a Flemish speaking psychologist. A back translation was provided by a second Flemish speaker. Independent native speakers reviewed the Flemish forward and backward translation and provided the pilot test version. The study design involved two phases: a focus group and cognitive debriefing phase with a pilot test and a field test with re-test phase. Within the focus groups/ cognitive debriefing in Belgium 18 children/adolescents and 26 parents discussed the pilot version.6 The focus group discussions were performed in cooperation with psychologists of the Department of Psychology and Educational Sciences of the Vrije Universiteit Brussel and of the Department of Endocrinology of the University Hospital of Gent. Age-specific child (8–12, 13–18 years) and parent (4– 7, 8–12, 13–18 years) focus group discussions were
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carried out together with a cognitive debriefing and pilot testing of the Flemish translated questionnaires (child and parent version). The most important aspects of quality of life of children with short stature were discussed during the first part of the focus groups. During the second part, children (8–18 years) and parents completed the QoLISSY instrument separately (pilot test) followed by a cognitive debriefing session. Each participant was asked to comment on their personal perceptions of the questions and their level of understanding. In addition, they were asked to evaluate the sensitivity, importance, clarity, and relevance of each item as it relates to their (or their child’s) height. No additional concepts or domains associated with QoL for both child and adolescent age group were identified in the focus groups and no further issues were identified by the cognitive debriefing panel. Since neither needs for adaptation nor for modifications in wording had been encountered, the pooled data from the pilot and the field test procedures were used in the validation analysis. For the field test, 18 additional children (8– 12 years; 13–18 years) and 27 parents (4–7 years; 8– 12 years; 13–18 years) were contacted via mail. The retest was distributed per mail with the request of completion within ten days (N523 children/adolescents and 32 parents).
Questionnaire scoring Based on the European QoLISSY Manual, the QoLISSY-QoL total score is calculated as mean of the core module.6 The 22 items QoLISSY-QoL core module includes three scales: Physical QoL (6 items), Social QoL (8 items) and Emotional QoL (8 items). Furthermore, three additional scales cover Treatment specific aspects (only for treated children; 14 items), aspects of Coping (10 items) and general Beliefs about height (5 items) as determinants of QoL. Two additional scales of the parent version contain questions about the child’s Future (4 items) and Effects of short stature on parents (11 items). A fivepoint Likert scale was used as a response scale ranging from 0 (‘not at all/never’) to 5 (‘extremely/ always’). Mean scores of each scale were calculated and transformed into values between 0 and 100, while higher values indicate a higher QoL. For validation purposes, children aged between 8 and 18 years also completed the KIDSCREEN 52 questionnaire, a wellvalidated and widely distributed generic HrQoL instrument.10 The KIDSCREEN 52 covers 10 domains: Physical Well-being (5 items), Psychological Well-being (6 items), Moods & Emotions (7 items), SelfPerception (5 items), Autonomy (5 items), Parent Relations & Home Life (6 items), Social Support &
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Peers (6 items), School Environment (6 Items), Social Acceptance (Bullying) (3 items), and Financial Resources (3 items). Socio-demographic data (e.g. gender and age) as well as clinical data (e.g. diagnosis, treatment status, duration of treatment, age at start of treatment) were gathered from child medical files. Height standard deviations scores were calculated using recent Flemish growth references.11
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Data analysis Scale characteristics such as mean (M) and standard deviation (SD) were examined together with floor and ceiling effects (percentage of responses at the lowest and highest scale end to describe the distribution or respondent responses in this sample). Cronbach’s Alpha was calculated for each domain and for the total score as an index of internal consistency. Test– retest reliability was assessed by calculation of the correlations for each time point for each domain and the total score for both the parents’ and the child’s version, using the Pearson’s correlation analysis. Convergent validity was assessed using the correlations between the QoLISSY and the KIDSCREEN 52 in the field test sample. Since the latter questionnaire was only distributed in the child version, correlations were only analysed between the QoLISSY child version and the KIDSCREEN 52 child version. Pearson’s correlations between QoLISSY scale scores of children and parents as well as the intraclass correlation coefficient between child and parent scores were calculated to examine concordance of ratings. The mean scale values of the Flemish sample were compared with the European sample using ttests (normal distribution was tested). In addition, correlations were calculated and compared using a Fisher z-transformation. Differences between gender (boy/girl) and age-group (4–7, 8–12, 13–18 years) as well as group differences according to diagnosis (ISS/ GHD), treatment status (treated/untreated), and degree of short stature ((22 SD, .2 SD) were analysed by non-parametric tests (Kruskal–Wallis test/Mann–Whitney U test). All statistical calculations were performed using the SPSS 18.0 software.11
Results Demographic characteristics From 56 families (one child and one parent) having agreed to participate in the field test, 54 families returned the questionnaires (4% drop-out). One questionnaire was excluded because of incompleteness. As a consequence, analyses are based on a total of 53 questionnaire sets: 36 parent’s and child’s versions from children aged more than 7 years and 17 parent’s versions of children aged between 4 and 7 years. Table 1 summarizes the demographic characteristics of the included children. Thirty-six boys
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Table 1 Demographic characteristics of the participating families (total sample) 4–7 years* 8–12 years 13–18 years Total n Gender Girl 7 Boy 10 Diagnosis GHD 5 ISS 12 Treatment status Untreated 10 GH-treated 7 Height SD (22 SDS 12 .22 SDS 5
%
n
%
n
%
n %
41.2 58.8
3 8
27.3 72.7
7 18
28.0 72.0
1732.1 3667.9
29.4 70.6
2 9
18.2 81.8
5 20
20.0 80.0
1222.6 4177.4
58.8 41.2
3 8
27.3 72.7
10 15
40.0 60.0
2343.4 3056.6
70.6 29.4
6 5
54.5 45.5
21 4
84.0 16.0
3973.6 1426.4
Note: *Only parents participated in the child’s age group 4– 7 years.
and 17 girls were included with more boys than girls in all age groups. Seventeen children were aged between 4 and 7 years, 11 between 8 and 12 years, and 25 between 13 and 18 years. Overall, 12 children were diagnosed with GHD and 41 with ISS. The distribution of treatment status was almost even (n untreated523 and n treated530). Although all children did meet the inclusion criteria at the time of diagnosis, 14 children were presently taller than 22 SD, while 39 children had a height SD below (22 SD at the time of analysis.
Reliability testing The scale means (M; on a scale 0–100 with 100 reflecting highest quality of life) ranged from 49.27 (Treatment) to 73.04 (Physical QoL) in the child’s version and from 46.68 (Coping) to 80.20 (Future) in the parent version. Overall mean scores identify a high level of subjective quality of life in young respondents, reaching about 73–80% of the scale with high standard deviations (SD) indicating substantive variance within the scales. Low floor (2.9–4.8% for children; 1.9–7.1% for parents) and low to moderate ceiling effects (2.9–22.9% for children; 2.0–22.4% for parents), as well as high reliabilities were observed for the overall data set. Cronbach‘s Alpha ranged from alpha50.80 (Physical QoL) to alpha50.94 (QoL total Score) for the child‘s version and from alpha50.77 (Physical QoL) to alpha50.92 (QoL total Score) for the parent’s version. The test–retest reliability was examined in 32 cases (60.4%) with completed retest questionnaires. Pearson correlation coefficients ranged from r50.75 (Physical QoL) to 0.89 (QoL total Score) in the child version and from r50.58 (Coping) to 0.85 (QoL total Score/Treatment/Emotional QoL) in the parent version.
Group comparison Neither the parent’s nor the child’s version revealed any significant gender differences, whereas significant
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differences were found between age groups: mean scores on the Beliefs scale were lower for older (M567.75; SD518.82) children compared to younger children (M586.25; SD518.82) in the child version (U(33)55.06; P50.024). In the parent’s version, scores were lower for older children (M585.91; SD516.40) on the Future scale as compared to younger children (M592.14; SD57.77) (H(2)510.38; P50.006).
Convergent validity testing
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Pearson’s correlation coefficients between QoLISSY and KIDSCREEN 52 were moderate to high between Social Acceptance (Bullying) and Social/Emotional in the QoLISSY child version (r50.54 and r50.48, see Table 4). Children with high scores on the QoLISSY coping module reported to get along well with their peers (Social Support & Peers r50.57) and did not perceive themselves as physically restricted (Physical Well-being r50.57). A high score on the QoLISSY Physical scale was also related to a high score on Autonomy and Self-Perception in the KIDSCREEN. The Self-Perception scale correlated with several QoLISSY scales. On the other hand, the correlations between the physical scales as well as the social scales of the two questionnaires were non-significant (Table 2).
Known groups differences Only the mean of the Coping scale in the child‘s questionnaire differed significantly between the two diagnostic groups: children with GHD scored lower on the Coping scale than children diagnosed with ISS (U(31)536.50; P50.045). On all other scales, children with GHD and ISS had similar results. When comparing untreated with GH treated children, no significant differences in any of the QoLISSY scales were found in both the parent’s and child’s versions. Regarding the degree of short stature, differences were found for the scales Physical QoL (PChildren50.004 and PParents50.004), Social QoL (PChildren50.008 and PParents50.017), Emotional QoL (PChildren50.015), Beliefs (PChildren50.002), Future (PParents50.032),
Effects on Parents (PParents50.047), and in the total QoL score (PChildren50.011 and PParents50.027), indicating that perceived QoL was higher for the less short children.
Child–parent concordance The parent’s version correlated significantly with the child’s version on all scales across families, with Pearson’s correlation (r) ranging from 0.48 (Physical) to 0.74 (Treatment). Within child parent pairs the intraclass correlation coefficient shows nearly the same results and ranges from r50.46 (Physical QoL) to 0.74 (Treatment).
Comparison with the international sample When comparing the Flemish sample (n553) with the original European sample (n5303), more ISS patients were included in Belgium (77.4%) than in the international sample (59.3%). In addition, more adolescents between 13 and 18 years were included in Belgium (69.4%) as compared to the international sample (51%). Treated and untreated children were equally represented in the samples. While in the international sample, the distribution across the height groups was comparable, more short children ((22 SDS) were included in the Belgian sample (73.6%). Nevertheless only the Effects on Parents scale in the parent’s version differed significantly between samples (t(75)52.87, P50.005), indicating a higher QoL for the Flemish sample (M571.29; SD520.06) concerning the Effects on Parents as compared to the international sample (M562.23; SD524.77). The comparison of Cronbach’s Alpha shows slightly higher values for internal consistency in the Flemish sample with alpha.0.80 for the scales of the QoLISSY core module as compared to the European sample (alpha.0.70). Examining the concordance between QoLISSY subscales by inter-scale correlations, the child’s versions showed significant correlations with similar correlation coefficients. Only two correlations that were significant in the European sample were not statistically significant in the Flemish sample (Treatment/Coping and Treatment/Beliefs). However,
Table 2 Correlation of the QoLISSY with the KIDSCREEN 52 (patient-report) scales Physical Social Emotional Coping Beliefs Treatment QoL total score KIDSCREEN 52 Physical well-being Psychological well-being Moods and emotions Self-perception Autonomy Parent relations and home life Financial resources Social support and peers School environment Social acceptance (bullying) Note: *P,0.05, **P,0.01.
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0.22 0.32 0.35 0.56** 0.47** .08 0.21 0.07 0.27 0.43*
0.37* 0.36* 0.37* 0.64** 0.22 0.09 0.42* 0.30 0.16 0.54**
0.26 0.39* 0.44* 0.68** 0.31 0.10 0.37* 0.30 0.33 0.48**
0.57** 0.45* 0.18 0.43* 0.27 0.27 0.17 0.57** 0.17 0.36*
.10 0.30 0.26 0.53** 0.38* 0.12 0.24 0.04 0.40* 0.15
0.24 0.06 20.17 0.07 0.22 0.08 20.11 0.22 20.16 20.07
0.29 0.41* 0.41* 0.67** 0.35* 0.11 0.36* 0.24 0.30 0.53*
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the correlation coefficients were similar (r50.23 versus r50.26 and r520.12 versus r520.18). The parent’s versions showed similar correlation coefficients as well. Compared to the European version, three correlations were not significant in the Flemish sample: between Physical and Treatment, Social and Treatment and the total score and Treatment. These correlation coefficients were small ranging from r50.21 to 0.25. The other correlation coefficients were similar and had the same direction (Table 3).
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Discussion Although a rather small convenience sample was used for the cultural adoption of the QoLISSY instrument for Flemish speaking children in Belgium, it was done by a sophisticated content-valid and robust procedure, as defined by the European QoLISSY Study Group.6 The validity of the multi-language QoLISSY instrument was previously confirmed by a satisfactory content, criterion, as well as construct validity in 268 children and 317 parents.6,7 The results of the pilot and field tests in 53 children and/or parents did provide an insight into important psychometric properties of the Flemish QoLISSY version, namely, reliability and validity. The internal consistencies were overall satisfactory with Cronbach’s alpha.0.70. The test–retest reliability was also acceptable with r values ranging from 0.75 to 0.89 in the child’s version and from 0.58 to 0.85 in the parent’s version. Overall, the Flemish version of the QoLISSY questionnaire can thus be considered a reliable instrument. Furthermore, the positive and statistically significant correlations between the QoLISSY and the KIDSCREEN 52 are an indication of its convergent validity. Moreover, high correlations were found between all QoLISSY scales and the KIDSCREEN Self-Perception domain, indicating that aspects measured by the QoLISSY reflect issues of selfperception. It must be stressed that physical items in QoLISSY questionnaire are height-related and thus, evaluate different aspects of physical well-being as compared to the KIDSCREEN scale. In contrast to the observed group validity in the European sample for the degree of shortness, treatment status, and diagnostic criteria, only a small impact of shortness was observed in the Flemish sample. This might be
QoLISSY Flemish version
related to the rather small sample size. On the other hand, children with ISS were overrepresented in our sample, in contrast to the European sample. The concordance between parent and child versions of the impact of short stature was reasonably high with few exceptions. However, as recommended by Matza et al.,8 the use of parental report of the child’s quality of life should be used with caution when self-report is unavailable (e.g. age) or the concept of interest is not directly observable (e.g. pain and emotional issues). In the case of the QoLISSY, the parent specific mediator domain of Effect on Parents provides a perspective not normally considered in measures of outcome in children. The authors recommend that the QoLISSY parent version can be used to supplement the information obtained directly from the child rather than to substitute for the child when measuring the child is possible. In spite of slight differences in the composition of samples, the distribution of scale scores within the Flemish and the original European QoLISSY instrument was comparable. Except for the Effects on Parents scale, agreement between the Flemish and the original European psychometric properties of the questionnaire was high. The inter-scale correlations were similar for the Flemish and the European questionnaire, suggesting comparable patterns of scale relationship. The small sample size and the cross-sectional design is a weakness of the Flemish validation study. In order to confirm the factorial validity with a confirmatory factor analysis, studies with larger samples including more families with short statured children (ISS/GHD) are needed. Nevertheless, the psychometric analyses of the Flemish QoLISSY field test yielded promising results. The Flemish QoLISSY version appears to be a reliable and valid instrument to assess QoL in children and adolescents referred to growth clinics for short stature due to idiopathic short stature or growth hormone deficiency and can be used in studies across Europe, including Belgium. The instrument is currently tested in a Dutch speaking sample of short statured children and adolescents in the Netherlands so that psychometric results can be compared within one language and across two countries.
Table 3 Inter-scale correlations between the Flemish and European sample (patient/parent-report) Scale
Physical
Social
Emotional
Coping
Beliefs
Treatment
QoL total score
Physical Social Emotional Coping Beliefs Treatment QoL total score
… 0.73**/0.78** 0.70**/0.63** 0.04/20.05 0.68**/0.58** 0.11/0.11 0.87**/0.90**
… 0.90**/0.78** 0.35/20.03 0.58**/0.56** 0.19/0.03 0.96**/0.95**
… 0.30/20.05 0.70**/0.54** 0.08/20.02 0.94**/0.86**
… 0.04/0.02 0.23/0.26** 0.23/20.05
… 20.12/20.18* 0.71**/0.62**
… 0.11/0.05
…
Note: *P,0.05, **P,0.01.
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Conflict of Interest
References
The project was funded by Pfizer and the authors were provided funding for its conduct at each site. There are no additional competing interests to report.
1 Bullinger M, Schmidt S, Petersen C, Erhart M, Ravens-Sieberer U. [Methodological challenges and potentials of health-related quality of life evaluation in children with chronic health conditions under medical health care]. Med Klin. 2007;102:734–45. German. 2 Bullinger M. Psychological criteria for treating children with idiopathic short stature. Horm Res Paediatr. 2011;76:20–3. 3 Chaplin JE. Growth-related quality of life. Horm Res Paediatr. 2011;76:51–2. 4 Noeker M. Psychological functioning in idiopathic short stature. Horm Res Paediatr. 2011;76:52–6. 5 Bru¨tt AL, Sandberg DE, Chaplin J, Wollmann H, Noeker M, Kołtowska-Ha¨ggstro¨m M, et al. Assessment of health-related quality of life and patient satisfaction in children and adolescents with growth hormone deficiency or idiopathic short stature — part 1: a critical evaluation of available tools. Horm Res. 2009;72:65–73. 6 The European QoLISSY Group. Quality of life in short stature youth. The QoLISSY questionnaire – user’s manual. Lengerich: Pabst Science Publishers; 2013. 7 Bullinger M, Quitmann J, Power M, Herdman M, Mimoun E, DeBusk K, et al. Assessing the quality of life of health-referred children and adolescents with short stature: development and psychometric testing of the QoLISSY instrument. Health Qual Life Outcomes. 2013;11:76. 8 Matza LS, Patrick DL, Riley AW, Alexander JJ, Rajmil L, Pleil AM, et al. Pediatric patient-reported outcome instruments for research to support medical product labeling: report of the ISPOR PRO Good Research Practices for the Assessment of Children and Adolescents Task Force. Value Health. 2013;16:461–79. 9 Kant SG, Wit JM, Breuning MH. Genetic analysis of short stature. Horm Res. 2003;60:157–65. 10 The KIDSCREEN Group Europe. The KIDSCREEN questionnaires: quality of life for children and adolescents — handbook. Lengerich: Pabst Science Publishers; 2006. 11 SPSS Inc. PASW for Windows, Version 18.0. Chicago, IL: SPSS Inc.; 2009.
Acknowledgements
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QoLISSY is a joint initiative between Pfizer and the University Medical Centre Hamburg–Eppendorf. Copyright Pfizer all rights reserved. The QoLISSY instrument, together with comprehensive information of its development and validation process, is published in the QoLISSY’s User’s Manual (Lengerich: Pabst Science Publishers; 2013). The QoLISSY study group, in addition to the German team of Monika Bullinger and Julia Quitmann (University Medical Centre Hamburg-Eppendorf, Department of Medical Psychology, Hamburg, Germany), includes John E. Chaplin (Sahlgrenska Academy at University of Gothenburg, Department of Paediatrics, Va¨xthuset, Queen Silvia’s Children’s Hospital, Gothenburg, Sweden), Michael Herdman (IMIM University, Insight Consulting and Research, Barcelona, Spain), Emmanuelle Mimoun (University of Toulouse, Department of Pediatric Endocrinology, Toulouse, France), Andreas Pleil (Pfizer, Inc. Specialty Care MDG, Outcomes Research, San Diego, CA), Hartmut Wollmann (University of Tuebingen), and Michael Power (University of Edinburgh, Department of Clinical Psychology, Edinburgh, Scotland).
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