http://informahealthcare.com/dre ISSN 0963-8288 print/ISSN 1464-5165 online Disabil Rehabil, 2015; 37(5): 411–416 ! 2014 Informa UK Ltd. DOI: 10.3109/09638288.2014.923524
RESEARCH PAPER
Validation of the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) in a sample of Dutch non-ambulatory children with cerebral palsy Trees A. L. Zalmstra1, Agnes Elema2, Anne M. Boonstra3, Karel G. B. Maathuis2, Unni G. Narayanan4,5, Annette A. J. v. d. Putten6, Heleen A. Reinders-Messelink2,3, Carla Vlaskamp6, and Robert Lindeboom7 1
Stichting Omega, Amsterdam, the Netherlands, 2Department of Rehabilitation Medicine, Centre for Rehabilitation, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands, 3Rehabilitation Centre ‘‘Revalidatie Friesland’’, Beetsterzwaag, the Netherlands, 4 Department of Surgery, University of Toronto, Toronto, Canada, 5Hospital for Sick Children, Toronto, Canada, 6Department of Special Needs Education and Child Care, University of Groningen, Groningen, the Netherlands, and 7Division of Clinical Methods and Public Health, Master Evidence Based Practice, Amsterdam, the Netherlands Abstract
Keywords
Purpose: To assess the reliability and validity of the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD)-Dutch Version, a proxy measure of health status and well-being of non-ambulatory children with cerebral palsy (CP). Methods: Parents (n ¼ 66) of 47 boys/19 girls between 5 and 18 years with CP (GMFCS IV–V) participated. To assess the reliability each domain and the total measure was tested for internal consistency, test–retest and inter-rater reliability. Known-groups validity of the CPCHILD-DV was assessed by comparing mean scores of clinically distinct subgroups and convergent validity by correlating the CPCHILD-DV with the TNO-AZL Preschool Children Quality of Life (TAPQOL). Results: The mean CPCHILD-DV total score was 52.0 (SD11.5). Test–retest reliability of the total score as assessed by intraclass correlations (ICC) was 0.73 (domains: 0.55–0.80). For the inter-rater reliability the ICC was 0.64 (domains: 0.58–0.90); the Cronbach’s alpha’s ranged from 0.60 to 0.95. The CPCHILD score could differentiate between GMFCS levels and between subgroups of cognitive level in the domain ‘‘communication and social interaction’’. There were moderate significant correlations (range rs: 0.31–0.50) between sections of CPCHILD-DV and TAPQOL. Conclusions: The CPCHILD-DV has sufficient reliability and validity as a proxy measure of health status and well-being of non-ambulatory children with CP.
Caregiver Priorities and Child Health Index of Life with Disabilities, children, health related quality of life, non-ambulatory children with cerebral palsy, validation History Received 8 September 2013 Revised 17 April 2014 Accepted 8 May 2014 Published online 26 May 2014
ä Implications for Rehabilitation
The Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) can be used to estimate health related quality of life of non-ambulatory children with cerebral palsy. The Dutch version of the CPCHILD has sufficient reliability and validity to be used as a proxy measure in research and clinical practice.
Introduction Cerebral Palsy (CP) is the most common cause of physical disability in children [1]. The Gross Motor Function Classification System (GMFCS) levels IV and V represent the non-ambulatory children (25% up to 35%) [2]. These children experience difficulties with their activities in daily life, communication, mobility and their health in such a way that they depend on their caregivers for the main part of their daily needs [3]. The focus of health care for these children is to limit the consequences of the disability and to improve comfort and quality of life.
Address for correspondence: Trees A. L. Zalmstra, Stichting Omega, F.D. Kahlenbergstraat 66, 1087 LL Amsterdam, the Netherlands. Tel: +31206994225. E-mail: [email protected]
Health-related quality of life (HRQL) has therefore been recognised as a key component to assess in non-ambulatory children with CP [4]. This outcome can be used on an individual level to guide treatment or to assess the effects of daily care and on a group level to establish the effects of interventions. Measuring HRQL in non-ambulatory children with CP is however challenging. Generic HRQL instruments, such as the Child Health Questionnaire (CHQ) [5] and the Pediatric Quality of Life Inventory (PedsQL) [6], do not adequately represent HRQL in non-ambulatory children with CP because they contain items which are not applicable to non-ambulatory children [7]. Other condition-specific instruments, e.g. Cerebral Palsy Quality Of Life (CPQOL) [8], Pediatric Outcome Data Collection Quality of Life (PODCI) [9], also assume higher intellectual or motor abilities. Domain specific instruments, such as the Pediatric Evaluation of Disability Inventory (PEDI) [10] or the Checklist
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Pain Behavior [11], lack important items e.g. comfort, emotions, and health issues. Available instruments such as the Caregiver Questionnaire (CQ) [12] and modified versions [13] lack data on their reliability and validity in non-ambulatory CP. Consequently, all these instruments are unlikely to be discriminative outcome measures for this specific population. Furthermore, because of cognitive and/or communicative restrictions, most nonambulatory children with CP are unable to express their perception of their health related quality of life. One is compelled to rely on parents or skilled caregivers (by proxy) as the closest possible approximation of the children’s HRQL. In 2006, a specific instrument for non-ambulatory children with CP was developed: the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) [3]. This proxy-measure has been designed to measure the caregivers’ perspectives on health status, functional limitations, comfort, well-being and ease of care giving of non-ambulatory children with CP aged between 5 and 18 years and was validated in a population of Canadian children. In the Netherlands, there is also need for a psychometrically sound proxy-instrument for HRQL in non-ambulatory children with CP. The aim of this study was to examine the reliability and validity of a Dutch version of this instrument (CPCHILD-DV) as a discriminative measure in a sample of Dutch non-ambulatory children with CP (GMFCS IV–V).
Methods Setting Between January and March 2011, the parents of non-ambulatory children with CP (GMFCS level IV–V) aged between 5 and 18 years, preferably two per child, were recruited from one academic centre, two rehabilitation centres, and two day-care centres for children with profound intellectual and motor disabilities. Eligible parents were responsible for the daily care of the child for at least the last 6 months and had sufficient comprehension of the Dutch language. All participating parents gave a written informed consent. The ethical review board at the University Medical Centre of Groningen approved the study. Sample size
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Table 1. Participants demographics. Child (n = 66) Boy: 47 Girl: 19 Age (years) Mean: 12 y, 2 mo (SD: 4 y) Min: 5 y Max: 18 y, 11 mo GMFCS level GMFCS IV: GMFCS V: unclear: Cognitive level I Very mild disability or normal intellectual function (IQ470): II Mild intellectual disability (IQ 50–70): III Developmental age 2–5 years: IV Developmental perspective 524 month: Unclear: Total score CPCHILD-DV (0–100) Mean: 52.0 (SD: 11.5) Min: 28.1 Max: 74.4 Total score TAPQOL (0–100) Median: 79.2 Interquartile range: 71.4–86.8 Caregiver A (n = 66) Mother: Father: Professional: Educational level High: Medium: Low: Missing: Age (years) Mean: 44 y, 4 mo (SD: 6 y, 4 mo) Min: 30 y Max: 60 y, 6 mo Caregiver B (n = 53) Father: Professional: Other relative: Mother: Age (years) Mean: 44 y, 10 mo (SD: 9 y) Min: 26 y, 6 mo Max: 63 y, 7 mo
29 (44%) 35 (53%) 2 (3%) 10 (15%) 8 (12%) 24 (37%) 22 (33%) 2 (3%)
62 (94%) 3 (5%) 1 (1%) 16 25 23 2
(24%) (38%) (35%) (3%)
43 5 3 2
(81%) (9%) (6%) (4%)
In a validation study, a sample size of 50–100 participants is generally recommended [14,15]. The original two validation studies of the CPCHILD included 52 and 67 participants, respectively [3,16]. To obtain a comparable sample size for this study, 125 parents received a written invitation to participate, of which 72 consented. During the study, there was a drop-out of six participants (death of child, family circumstances, non-response). Post-hoc sample size calculations indicated that with the included n ¼ 66 a difference in means of two groups on the CPCHILD of 8.0 points could be statistically detected (at p ¼ 0.05 and a power of 80%) and a difference in means characterised by a variance of means of 24.0 in the analysis of variance (ANOVA). With the same sample size, a correlation coefficient of 0.35 could be statistically detected using a Fisher’s z test for a Pearson correlation coefficient different from zero under the same study reliability requirements.
The TAPQOL total score was skewed to the right. Two percent of the sample had a maximum score on the TAPQOL. Participants were a convenience sample of eligible families. Although CP is more common among boys than girls (in Europe ratio 1.3: 1 [17], it does not fully explain the high boy/girl ratio. We expect this to be a result of chance.
Participants
Measure
Table 1 shows the participant demographics. Parents (mostly mothers) of 66 children participated in the study, of which 62 completed the second questionnaire. In addition, 53 other caregivers in the family (mostly fathers) completed the questionnaire independently on the first occasion. The total score of the CPCHILD was approximately normally distributed. None of the participants achieved the lowest or highest possible score.
The CPCHILD consists of 37 items across six domains: ‘‘personal care/activities of daily living’’, ‘‘positioning, transferring and mobility’’, ‘‘comfort and emotions’’, ‘‘communication and social interaction’’, ‘‘health’’, ‘‘overall quality of life’’. Each item is rated on a 6- or 7-point scale and for some items in addition a 4-point level of assistance modifier. Transformed scores from 0 (worst) to 100 (best) are calculated for each of the six domains,
y, year; mo, months; GMFCS, Gross Motor Function Classification System; IQ, intelligence quotient; SD, standard deviation; Min, minimum; Max, maximum.
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and for the total instrument. These scores were derived from the raw item scores divided by the maximum item score, multiplied by 100. The questionnaire takes 20–30 min to complete. Crosscultural transformation into the Dutch language and culture was performed according to the methods and criteria of Swaine Verdier for adapting QOL-instruments [18]. First a translation of the CPCHILD was developed by three subgroups (of medical, orthopedagogic and physiotherapeutic background) independently and then the subgroups reached consensus. The agreed translated version was assessed by a lay panel (seven people with different professional backgrounds) working as a focus group, which had access only to the translated version. Two coordinators from the research group ensured that the original meaning of items and questionnaire structure were maintained. Special attention was given to clear wording due to the multiethnic population of the Netherlands. The adapted translation was then tested by means of one-to-one interviews with 15 parents of non-ambulatory children with CP. These parents were not included in the reliability and validity study. The whole procedure was reported in detail. Assessment of reliability Test–retest reliability was assessed by administering the CPCHILD-DV by mail to parents on two separate occasions approximately 2 weeks apart [3]. Inter-rater reliability was assessed by comparing the CPCHILD-scores of two parents of the same child who were instructed to independently complete the CPCHILD-DV on the same day. Assessment of validity Content validity of the CPCHILD-DV was assessed by the parent’s rating of the importance of each item’s contribution to their child’s HRQL on a 6-point scale from 0 (least important) to 5 (most important). The threshold value was set at a median of 2. Known groups validity of the CPCHILD-DV as a discriminative measure of HRQL was assessed by comparing the scores of the CPCHILD-DV of children in GMFCS level V (poorer motor function) and those in GMFCS level IV, who were expected to have significantly higher CPCHILD scores [3]. We also compared the mean CPCHILD-scores of children of four cognitive levels: I ‘‘very mild intellectual disability or normal intellectual function (IQ470)’’, II ‘‘mild intellectual disability (IQ 50–70)’’, III ‘‘severe to moderate intellectual disability (developmental age 2–5 years)’’, IV ‘‘profound intellectual and multiple disabilities (developmental perspective 524 month)’’. Based on previous studies [19] children with a higher cognitive level were expected to have significantly higher CPCHILD-scores, especially in the domain ‘‘communication and social interaction’’. Furthermore, convergent validity was assessed by comparing the CPCHILD-scores with the scores of the TNO-AZL Preschool Children Quality of Life (TAPQOL), an established generic HRQL-measure for chronically-ill children [20], which was administered to the parents in conjunction with the
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CPCHILD-DV. Psychometric evaluation in a Dutch sample supported the TAPQOL’s reliability and discriminative validity for the majority of its scales (Cronbach’s 40.70 in 9 of the 13 scales; test–retest reliability showed no significant differences in mean scale scores; five scales showed significant differences between children with no conditions versus children with two or more chronic conditions) [21]. The TAPQOL was chosen from the few Dutch validated proxy HRQL-measures for children as a comparable measure, because of the similar phrasing of the questions (asking how difficult certain activities are for the child). The preschool version was used, in consultation with the developers, because of the expected low average cognitive level and low level of self care of the majority of the children. We correlated the CPCHILD total scores and domain scores with the TAPQOL total score as an overall measure of HRQL. Given the generic nature of the TAPQOL, we expected moderately strong correlations (around 0.50). Statistical analysis Data were analysed using SPSS for Windows (version 17). Test–retest and inter-rater reliability was estimated by using the intraclass correlation coefficient (ICC case 1, single measure) including 95% confidence intervals (CI). ICCs ranging from 0 to 0.20 were considered poor, from 0.21 to 0.40 fair, 0.41 to 0.60 moderate, 0.61 to 0.80 good, and from 0.81 to 1.00 excellent [22]. The method of Bland and Altman was used to assess the magnitude of the measurement error and to calculate limits of agreement [23]. The internal consistency of the CPCHILD at baseline was assessed by calculating Cronbach alpha coefficients. Alpha coefficients between 0.70 and 0.95 for all domains were considered adequate [15]. The mean domain and total scores of children with GMFCS level IV and V of the four cognitive development groups were compared with independent sample t-test and ANOVA, respectively. Convergent validity was estimated by Spearman’s rank correlation coefficients (rs). We used parametric tests for the CPCHILD because the scores had an approximately normal distribution. Since the TAPQOL-scores were skewed to the right, we used non-parametric test for these analyses. The significance level was set at p50.05 two-tailed.
Results Reliability The ICC for the test–retest reliability of the CPCHILD-DV total score (n ¼ 62) was 0.73 and ranged from 0.55 to 0.80 for the domains (Table 2). The Bland and Altman plot showed that the measurement error was random and 95% of the scores, the limits of agreement, ranged between ± 16.9 points of the mean difference. Systematic error was small (mean 1.9 points) and not significant (Figure 1). For the inter-rater reliability, the ICC for the total score was 0.64 and ranged from 0.58 to 0.90 for the domains (Table 2). The Bland and Altman plot showed again that the measurement
Table 2. Reliability of the CPCHILD domain scores and total score. Domains CPCHILD-DV (# items) Personal care/activities of daily living (9) Positioning, transferring and mobility (8) Comfort and emotions (9) Communication and social interaction (7) Health (3) Overall quality of life (1) Total score (37) a
Test–retest ICC (n ¼ 62)
95% CI
Inter-rater ICC (n ¼ 53)
95% CI
a
0.55 0.60 0.80 0.71 0.76 0.65 0.73
0.34–0.70 0.41–0.74 0.70–0.88 0.57–0.82 0.64–0.85 0.48–0.77 0.59–0.83
0.74 0.62 0.62 0.75 0.90 0.58 0.64
0.58–0.85 0.42–0.77 0.42–0.76 0.60–0.85 0.84–0.94 0.37–0.74 0.45–0.78
0.95 0.79 0.91 0.84 0.60
No Cronbach a since only one item; ICC, intraclass correlation coefficient; CI, confidence interval.
a
0.89
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Figure 1. Bland and Altman plot of the test–retest reliability of the total score.
Figure 2. Bland and Altman plot of the inter-rater reliability of the total score.
error was random and 95% of the scores, the limits of agreement, ranged between ± 20.0 points of the mean difference. Systematic error was small (mean 1.1 points) and not significant (Figure 2). Internal consistencies for the domain scores and total scores were over 0.70 except for the health domain (0.60) that has only 3 items (Table 2). The data showed irregularities in two domains: ‘‘personal care/ activities of daily living’’ and ‘‘positioning, transferring and mobility’’, in which activities are scored on the level of assistance needed and on the degree of difficulty of accomplishing the activity by/for the child. When the child needs total assistance, one should score the degree of difficulty of accomplishing the activity for the child. Some participants however rated, when the child needed total assistance, the degree of difficulty of
accomplishing an activity (e.g. eating/drinking) as ‘‘impossible’’. This led to exceedingly low scores on these two domains (11), which is technically impossible, since these domains concern everyday activities. This seems to be an interpretation error. These errors (by 12 participants) can have an impact on the results. For instance the ICC for the test–retest reliability of the total score calculated without these cases changed from 0.73 to 0.81 (95% CI: 0.70–0.89), the mean systematic error in the Bland and Altman plot from 1.9 to 1.6 points and the 95% limits of agreement from ±16.9 to ±13.6 points. Content and construct validity Of the 36 evaluated CPCHILD-DV items, two had a median score of 3 (fairly important), 27 had a median score of 4
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Table 3. Known groups comparison in CPCHILD-scores in motor levels and cognitive levels. GMFCS levels IV n ¼ 29 Personal care/activities of daily living Positioning, transferring and mobility Comfort and emotions Communication and social interaction Health Overall quality of life Total
39.2 39.8 78.1 63.6 67.7 65.3 56.8
V n ¼ 35
(16.0) (10.7) (19.6) (17.7) (22.2) (17.4) (10.7)
28.7 32.7 76.6 46.2 64.1 61.7 47.9
(16.4) (14.7) (21.2) (21.3) (17.8) (16.8) (10.6)
Cognitive levels p Valuea 0.01 0.04 0.76 50.001 0.47 0.39 50.001
I n ¼ 10 34.9 41.7 72.8 72.4 64.7 62.0 55.7
(17.3) (8.4) (22.6) (14.1) (29.7) (17.5) (9.8)
II n¼8 34.7 36.6 79.0 68.2 73.3 77.5 56.8
(17.6) (18.5) (22.1) (22.7) (17.5) (19.8) (14.8)
III n ¼ 24 30.9 33.6 75.4 53.1 71.4 64.3 50.8
(18.1) (11.8) (19.4) (17.3) (18.6) (15.9) (10.8)
IV n ¼ 22 35.5 34.8 82.0 40.6 57.0 60.0 49.2
(16.2) (14.7) (19.6) (18.3) (14.2) (15.1) (11.2)
p Valueb 0.82 0.45 0.59 50.001 0.05 0.09 0.29
All scores are means (SD). GMFCS, Gross Motor Function Classification System: aIndependent sample t-test, bOne-way analysis of variance.
Table 4. Spearman’s rho correlation coefficients between CPCHILD scores and TAPQOL total score. CPCHILD scores
TAPQOL total score
Personal care/activities of daily living Positioning, transferring and mobility Comfort and emotions Communication and social interaction Health Overall quality of life Total
0.09 0.22 0.44a 0.50a 0.39a 0.41a 0.50a
a
Correlation is significant at the 0.01 level (two-tailed).
(very important) and seven had a score of 5 (most important). Table 3 shows the known group validation results. Children in GMFCS level V (poorer motor function) had a significantly lower mean total score on the CPCHILD-DV than those in GMFCS level IV (mean difference 8.9 points (95% CI: 3.6–14.2); p50.001). At domain level there was a statistically significant difference in the domains ‘‘personal care/activities of daily living’’ (10.5 points, 95% CI: 2.4–18.6), ‘‘positioning, transferring and mobility’’ (7.1 points, 95% CI: 0.5–13.6) and ‘‘communication and social interaction’’ (17.4 points, 95% CI: 7.6–27.1). The differences between the four cognitive level groups were only statistically significant in the domain ‘‘communication and social interaction’’ (F: 9.3; df: 3; p50.01). The post-hoc pairwise comparisons (Bonferroni corrected) revealed a statistical significance (p50.01) between the lowest cognitive level IV and each of the two highest levels (II and I, mean difference 27.5 and 31.8 points, respectively). Except for the domains ‘‘personal care/ activities of daily living’’ and ‘‘positioning, transferring and mobility’’, all CPCHILD domain scores (rs from 0.39 to 0.50) and total score (rs ¼ 0.50) were significantly correlated with the TAPQOL (Table 4).
Discussion Our study showed that the CPCHILD is a psychometrically sound proxy-instrument to discriminate between HRQL levels in Dutch non-ambulatory children with CP. The distribution of scores was similar as that observed in the original validation study of the CPCHILD [16]. The internal consistency was high except for one domain, which consists of only 3 items. The test–retest reliability coefficients were in the ‘‘good’’ range, (40.60 [22]) for four domains and the total score and were moderate for two domains (‘‘personal care/activities of daily living’’ and ‘‘positioning, transferring and mobility’’). For the inter-rater reliability, two of the subscales (‘‘positioning, transferring and mobility’’ and ‘‘comfort and emotions’’) and the total score were just above 0.60 and the ICC of ‘‘overall quality of life’’ domain just under
0.60. Although this indicates a ‘‘moderate/good’’ reliability, this result suggests that the CPCHILD-DV, being a proxy instrument, should be preferably administered by the same parent. The measurement error was random with a small systematic error. The original validation study of the CPCHILD showed slightly higher ICCs for the test–retest reliability (ICC total score: 0.85, ICC domains from 0.59 to 0.87) [16]. However, after correction for interpretation errors by some parents (as explained in ‘‘Results, reliability’’), the ICCs were comparable (ICC total score: 0.81, ICC domains from 0.61 to 0.81). This shows that the interpretation errors have a negative impact on the reliability. The occurrence of interpretation errors in this study may be a result of the mode of administration. Questionnaires were sent to the parents to complete at home while in the original study a verbal instruction was provided to the parents. The following results demonstrated the validity of the CPCHILD-DV: there were no floor and ceiling effects, which indicate that this measure is appropriate for the target population and that a good differentiation between the children is possible. Parents rated all items more than sufficiently important, thereby confirming the content validity. As hypothesised, there were significant differences in CPCHILD scores of motor function level (GMFCS) groups. Similar results were found in the original validation study. The differences between the four cognitive levels were – as hypothesised – significant in the domain ‘‘communication and social interaction’’. Convergent validity of the CPCHILD-DV was supported by moderate correlation with the TAPQOL, as was expected. However, the CPCHILD domains ‘‘personal care/activities of daily living’’ and ‘‘positioning, transferring and mobility’’, which were especially developed for non-ambulatory children, had low and insignificant correlations with the TAPQOL total score. This may be the results of the TAPQOL being a generic measure and designed for chronically-ill children in general. The skewed distribution of the TAPQOL scores, for which the TAPQOL is known [21], shows that this measure is not appropriate to discriminate between HRQL levels in non-ambulatory children with CP. In another study, with CP-children the TAPQOL also showed ceiling effects [24]. The results of the convergent validation are fairly similar to those in the original study, in which the total and domain scores were compared with the physical and psychosocial summary scores of the CHQ, a generic measure. The Spearman’s rank correlation in that study ranged from 0.22 to 0.67, 50% was significant and three out of 14 coefficients were 40.50. A limitation of this study was that the generic TAPQOL was the best available measure to evaluate convergence. In the view of the limited variation on the TAPQOL in this specific population, no optimal evaluation of convergent validity was possible. Future studies examining the relation of the CPCHILD scores with other patient variables to further corroborate the instrument’s validity
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are recommended. Furthermore, the instruction for two domains was unclear to some people, and this led to interpretation errors. Editing of the instructions is important and may enhance the reliability. We also decided to add a relevant example to the instruction to avoid errors of interpretation. Because the questionnaires were sent home, with no researcher present, it cannot be guaranteed that the two parents for the same child completed the questionnaires independently. This may have led to an overestimation of the ICCs of the inter-rater reliability. It would have been better to administer the questionnaires at the clinic in separate rooms or in presence of a researcher. However this was, due to practical and organisational reasons, not possible. Instead, we stressed the importance of independent completion to parents as copying each others answers would compromise the study. Another issue is the question whether a proxy-instrument can measure HRQL accurately. This point was also addressed in the original validation study [3]. The best way to measure HRQL is directly from the child, since it has been established that differences can exist in proxy-agreement of child and parent on an individual level [25]. If this is not possible, as is the case in severely disabled children, the next best way (especially at grouplevel) is relying on the perspectives of the parents. In conclusion, this study has shown that the CPCHILD-DV has sufficient reliability and validity as a proxy measure of health status and well-being of non-ambulatory children with CP. Further studies on the sensitivity to change are needed before this instrument can be recommended for use as an outcome measure.
Acknowledgements
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7. 8. 9.
10. 11. 12.
13. 14.
15. 16.
The authors would like to thank the families who participated in this study.
Declaration of interest
17.
The authors report no conflicts of interest.
18.
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Validation of the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) in a sample of Dutch non-ambulatory children with cerebral palsy Trees A. L. Zalmstra1, Agnes Elema2, Anne M. Boonstra3, Karel G. B. Maathuis2, Unni G. Narayanan4,5, Annette A. J. v. d. Putten6, Heleen A. Reinders-Messelink2,3, Carla Vlaskamp6, and Robert Lindeboom7 1
Stichting Omega, Amsterdam, the Netherlands, 2Department of Rehabilitation Medicine, Centre for Rehabilitation, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands, 3Rehabilitation Centre ‘‘Revalidatie Friesland’’, Beetsterzwaag, the Netherlands, 4 Department of Surgery, University of Toronto, Toronto, Canada, 5Hospital for Sick Children, Toronto, Canada, 6Department of Special Needs Education and Child Care, University of Groningen, Groningen, the Netherlands, and 7Division of Clinical Methods and Public Health, Master Evidence Based Practice, Amsterdam, the Netherlands Abstract
Keywords
Purpose: To assess the reliability and validity of the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD)-Dutch Version, a proxy measure of health status and well-being of non-ambulatory children with cerebral palsy (CP). Methods: Parents (n ¼ 66) of 47 boys/19 girls between 5 and 18 years with CP (GMFCS IV–V) participated. To assess the reliability each domain and the total measure was tested for internal consistency, test–retest and inter-rater reliability. Known-groups validity of the CPCHILD-DV was assessed by comparing mean scores of clinically distinct subgroups and convergent validity by correlating the CPCHILD-DV with the TNO-AZL Preschool Children Quality of Life (TAPQOL). Results: The mean CPCHILD-DV total score was 52.0 (SD11.5). Test–retest reliability of the total score as assessed by intraclass correlations (ICC) was 0.73 (domains: 0.55–0.80). For the inter-rater reliability the ICC was 0.64 (domains: 0.58–0.90); the Cronbach’s alpha’s ranged from 0.60 to 0.95. The CPCHILD score could differentiate between GMFCS levels and between subgroups of cognitive level in the domain ‘‘communication and social interaction’’. There were moderate significant correlations (range rs: 0.31–0.50) between sections of CPCHILD-DV and TAPQOL. Conclusions: The CPCHILD-DV has sufficient reliability and validity as a proxy measure of health status and well-being of non-ambulatory children with CP.
Caregiver Priorities and Child Health Index of Life with Disabilities, children, health related quality of life, non-ambulatory children with cerebral palsy, validation History Received 8 September 2013 Revised 17 April 2014 Accepted 8 May 2014 Published online 26 May 2014
ä Implications for Rehabilitation
The Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) can be used to estimate health related quality of life of non-ambulatory children with cerebral palsy. The Dutch version of the CPCHILD has sufficient reliability and validity to be used as a proxy measure in research and clinical practice.
Introduction Cerebral Palsy (CP) is the most common cause of physical disability in children [1]. The Gross Motor Function Classification System (GMFCS) levels IV and V represent the non-ambulatory children (25% up to 35%) [2]. These children experience difficulties with their activities in daily life, communication, mobility and their health in such a way that they depend on their caregivers for the main part of their daily needs [3]. The focus of health care for these children is to limit the consequences of the disability and to improve comfort and quality of life.
Address for correspondence: Trees A. L. Zalmstra, Stichting Omega, F.D. Kahlenbergstraat 66, 1087 LL Amsterdam, the Netherlands. Tel: +31206994225. E-mail: [email protected]
Health-related quality of life (HRQL) has therefore been recognised as a key component to assess in non-ambulatory children with CP [4]. This outcome can be used on an individual level to guide treatment or to assess the effects of daily care and on a group level to establish the effects of interventions. Measuring HRQL in non-ambulatory children with CP is however challenging. Generic HRQL instruments, such as the Child Health Questionnaire (CHQ) [5] and the Pediatric Quality of Life Inventory (PedsQL) [6], do not adequately represent HRQL in non-ambulatory children with CP because they contain items which are not applicable to non-ambulatory children [7]. Other condition-specific instruments, e.g. Cerebral Palsy Quality Of Life (CPQOL) [8], Pediatric Outcome Data Collection Quality of Life (PODCI) [9], also assume higher intellectual or motor abilities. Domain specific instruments, such as the Pediatric Evaluation of Disability Inventory (PEDI) [10] or the Checklist
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Pain Behavior [11], lack important items e.g. comfort, emotions, and health issues. Available instruments such as the Caregiver Questionnaire (CQ) [12] and modified versions [13] lack data on their reliability and validity in non-ambulatory CP. Consequently, all these instruments are unlikely to be discriminative outcome measures for this specific population. Furthermore, because of cognitive and/or communicative restrictions, most nonambulatory children with CP are unable to express their perception of their health related quality of life. One is compelled to rely on parents or skilled caregivers (by proxy) as the closest possible approximation of the children’s HRQL. In 2006, a specific instrument for non-ambulatory children with CP was developed: the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) [3]. This proxy-measure has been designed to measure the caregivers’ perspectives on health status, functional limitations, comfort, well-being and ease of care giving of non-ambulatory children with CP aged between 5 and 18 years and was validated in a population of Canadian children. In the Netherlands, there is also need for a psychometrically sound proxy-instrument for HRQL in non-ambulatory children with CP. The aim of this study was to examine the reliability and validity of a Dutch version of this instrument (CPCHILD-DV) as a discriminative measure in a sample of Dutch non-ambulatory children with CP (GMFCS IV–V).
Methods Setting Between January and March 2011, the parents of non-ambulatory children with CP (GMFCS level IV–V) aged between 5 and 18 years, preferably two per child, were recruited from one academic centre, two rehabilitation centres, and two day-care centres for children with profound intellectual and motor disabilities. Eligible parents were responsible for the daily care of the child for at least the last 6 months and had sufficient comprehension of the Dutch language. All participating parents gave a written informed consent. The ethical review board at the University Medical Centre of Groningen approved the study. Sample size
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Table 1. Participants demographics. Child (n = 66) Boy: 47 Girl: 19 Age (years) Mean: 12 y, 2 mo (SD: 4 y) Min: 5 y Max: 18 y, 11 mo GMFCS level GMFCS IV: GMFCS V: unclear: Cognitive level I Very mild disability or normal intellectual function (IQ470): II Mild intellectual disability (IQ 50–70): III Developmental age 2–5 years: IV Developmental perspective 524 month: Unclear: Total score CPCHILD-DV (0–100) Mean: 52.0 (SD: 11.5) Min: 28.1 Max: 74.4 Total score TAPQOL (0–100) Median: 79.2 Interquartile range: 71.4–86.8 Caregiver A (n = 66) Mother: Father: Professional: Educational level High: Medium: Low: Missing: Age (years) Mean: 44 y, 4 mo (SD: 6 y, 4 mo) Min: 30 y Max: 60 y, 6 mo Caregiver B (n = 53) Father: Professional: Other relative: Mother: Age (years) Mean: 44 y, 10 mo (SD: 9 y) Min: 26 y, 6 mo Max: 63 y, 7 mo
29 (44%) 35 (53%) 2 (3%) 10 (15%) 8 (12%) 24 (37%) 22 (33%) 2 (3%)
62 (94%) 3 (5%) 1 (1%) 16 25 23 2
(24%) (38%) (35%) (3%)
43 5 3 2
(81%) (9%) (6%) (4%)
In a validation study, a sample size of 50–100 participants is generally recommended [14,15]. The original two validation studies of the CPCHILD included 52 and 67 participants, respectively [3,16]. To obtain a comparable sample size for this study, 125 parents received a written invitation to participate, of which 72 consented. During the study, there was a drop-out of six participants (death of child, family circumstances, non-response). Post-hoc sample size calculations indicated that with the included n ¼ 66 a difference in means of two groups on the CPCHILD of 8.0 points could be statistically detected (at p ¼ 0.05 and a power of 80%) and a difference in means characterised by a variance of means of 24.0 in the analysis of variance (ANOVA). With the same sample size, a correlation coefficient of 0.35 could be statistically detected using a Fisher’s z test for a Pearson correlation coefficient different from zero under the same study reliability requirements.
The TAPQOL total score was skewed to the right. Two percent of the sample had a maximum score on the TAPQOL. Participants were a convenience sample of eligible families. Although CP is more common among boys than girls (in Europe ratio 1.3: 1 [17], it does not fully explain the high boy/girl ratio. We expect this to be a result of chance.
Participants
Measure
Table 1 shows the participant demographics. Parents (mostly mothers) of 66 children participated in the study, of which 62 completed the second questionnaire. In addition, 53 other caregivers in the family (mostly fathers) completed the questionnaire independently on the first occasion. The total score of the CPCHILD was approximately normally distributed. None of the participants achieved the lowest or highest possible score.
The CPCHILD consists of 37 items across six domains: ‘‘personal care/activities of daily living’’, ‘‘positioning, transferring and mobility’’, ‘‘comfort and emotions’’, ‘‘communication and social interaction’’, ‘‘health’’, ‘‘overall quality of life’’. Each item is rated on a 6- or 7-point scale and for some items in addition a 4-point level of assistance modifier. Transformed scores from 0 (worst) to 100 (best) are calculated for each of the six domains,
y, year; mo, months; GMFCS, Gross Motor Function Classification System; IQ, intelligence quotient; SD, standard deviation; Min, minimum; Max, maximum.
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DOI: 10.3109/09638288.2014.923524
and for the total instrument. These scores were derived from the raw item scores divided by the maximum item score, multiplied by 100. The questionnaire takes 20–30 min to complete. Crosscultural transformation into the Dutch language and culture was performed according to the methods and criteria of Swaine Verdier for adapting QOL-instruments [18]. First a translation of the CPCHILD was developed by three subgroups (of medical, orthopedagogic and physiotherapeutic background) independently and then the subgroups reached consensus. The agreed translated version was assessed by a lay panel (seven people with different professional backgrounds) working as a focus group, which had access only to the translated version. Two coordinators from the research group ensured that the original meaning of items and questionnaire structure were maintained. Special attention was given to clear wording due to the multiethnic population of the Netherlands. The adapted translation was then tested by means of one-to-one interviews with 15 parents of non-ambulatory children with CP. These parents were not included in the reliability and validity study. The whole procedure was reported in detail. Assessment of reliability Test–retest reliability was assessed by administering the CPCHILD-DV by mail to parents on two separate occasions approximately 2 weeks apart [3]. Inter-rater reliability was assessed by comparing the CPCHILD-scores of two parents of the same child who were instructed to independently complete the CPCHILD-DV on the same day. Assessment of validity Content validity of the CPCHILD-DV was assessed by the parent’s rating of the importance of each item’s contribution to their child’s HRQL on a 6-point scale from 0 (least important) to 5 (most important). The threshold value was set at a median of 2. Known groups validity of the CPCHILD-DV as a discriminative measure of HRQL was assessed by comparing the scores of the CPCHILD-DV of children in GMFCS level V (poorer motor function) and those in GMFCS level IV, who were expected to have significantly higher CPCHILD scores [3]. We also compared the mean CPCHILD-scores of children of four cognitive levels: I ‘‘very mild intellectual disability or normal intellectual function (IQ470)’’, II ‘‘mild intellectual disability (IQ 50–70)’’, III ‘‘severe to moderate intellectual disability (developmental age 2–5 years)’’, IV ‘‘profound intellectual and multiple disabilities (developmental perspective 524 month)’’. Based on previous studies [19] children with a higher cognitive level were expected to have significantly higher CPCHILD-scores, especially in the domain ‘‘communication and social interaction’’. Furthermore, convergent validity was assessed by comparing the CPCHILD-scores with the scores of the TNO-AZL Preschool Children Quality of Life (TAPQOL), an established generic HRQL-measure for chronically-ill children [20], which was administered to the parents in conjunction with the
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CPCHILD-DV. Psychometric evaluation in a Dutch sample supported the TAPQOL’s reliability and discriminative validity for the majority of its scales (Cronbach’s 40.70 in 9 of the 13 scales; test–retest reliability showed no significant differences in mean scale scores; five scales showed significant differences between children with no conditions versus children with two or more chronic conditions) [21]. The TAPQOL was chosen from the few Dutch validated proxy HRQL-measures for children as a comparable measure, because of the similar phrasing of the questions (asking how difficult certain activities are for the child). The preschool version was used, in consultation with the developers, because of the expected low average cognitive level and low level of self care of the majority of the children. We correlated the CPCHILD total scores and domain scores with the TAPQOL total score as an overall measure of HRQL. Given the generic nature of the TAPQOL, we expected moderately strong correlations (around 0.50). Statistical analysis Data were analysed using SPSS for Windows (version 17). Test–retest and inter-rater reliability was estimated by using the intraclass correlation coefficient (ICC case 1, single measure) including 95% confidence intervals (CI). ICCs ranging from 0 to 0.20 were considered poor, from 0.21 to 0.40 fair, 0.41 to 0.60 moderate, 0.61 to 0.80 good, and from 0.81 to 1.00 excellent [22]. The method of Bland and Altman was used to assess the magnitude of the measurement error and to calculate limits of agreement [23]. The internal consistency of the CPCHILD at baseline was assessed by calculating Cronbach alpha coefficients. Alpha coefficients between 0.70 and 0.95 for all domains were considered adequate [15]. The mean domain and total scores of children with GMFCS level IV and V of the four cognitive development groups were compared with independent sample t-test and ANOVA, respectively. Convergent validity was estimated by Spearman’s rank correlation coefficients (rs). We used parametric tests for the CPCHILD because the scores had an approximately normal distribution. Since the TAPQOL-scores were skewed to the right, we used non-parametric test for these analyses. The significance level was set at p50.05 two-tailed.
Results Reliability The ICC for the test–retest reliability of the CPCHILD-DV total score (n ¼ 62) was 0.73 and ranged from 0.55 to 0.80 for the domains (Table 2). The Bland and Altman plot showed that the measurement error was random and 95% of the scores, the limits of agreement, ranged between ± 16.9 points of the mean difference. Systematic error was small (mean 1.9 points) and not significant (Figure 1). For the inter-rater reliability, the ICC for the total score was 0.64 and ranged from 0.58 to 0.90 for the domains (Table 2). The Bland and Altman plot showed again that the measurement
Table 2. Reliability of the CPCHILD domain scores and total score. Domains CPCHILD-DV (# items) Personal care/activities of daily living (9) Positioning, transferring and mobility (8) Comfort and emotions (9) Communication and social interaction (7) Health (3) Overall quality of life (1) Total score (37) a
Test–retest ICC (n ¼ 62)
95% CI
Inter-rater ICC (n ¼ 53)
95% CI
a
0.55 0.60 0.80 0.71 0.76 0.65 0.73
0.34–0.70 0.41–0.74 0.70–0.88 0.57–0.82 0.64–0.85 0.48–0.77 0.59–0.83
0.74 0.62 0.62 0.75 0.90 0.58 0.64
0.58–0.85 0.42–0.77 0.42–0.76 0.60–0.85 0.84–0.94 0.37–0.74 0.45–0.78
0.95 0.79 0.91 0.84 0.60
No Cronbach a since only one item; ICC, intraclass correlation coefficient; CI, confidence interval.
a
0.89
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Figure 1. Bland and Altman plot of the test–retest reliability of the total score.
Figure 2. Bland and Altman plot of the inter-rater reliability of the total score.
error was random and 95% of the scores, the limits of agreement, ranged between ± 20.0 points of the mean difference. Systematic error was small (mean 1.1 points) and not significant (Figure 2). Internal consistencies for the domain scores and total scores were over 0.70 except for the health domain (0.60) that has only 3 items (Table 2). The data showed irregularities in two domains: ‘‘personal care/ activities of daily living’’ and ‘‘positioning, transferring and mobility’’, in which activities are scored on the level of assistance needed and on the degree of difficulty of accomplishing the activity by/for the child. When the child needs total assistance, one should score the degree of difficulty of accomplishing the activity for the child. Some participants however rated, when the child needed total assistance, the degree of difficulty of
accomplishing an activity (e.g. eating/drinking) as ‘‘impossible’’. This led to exceedingly low scores on these two domains (11), which is technically impossible, since these domains concern everyday activities. This seems to be an interpretation error. These errors (by 12 participants) can have an impact on the results. For instance the ICC for the test–retest reliability of the total score calculated without these cases changed from 0.73 to 0.81 (95% CI: 0.70–0.89), the mean systematic error in the Bland and Altman plot from 1.9 to 1.6 points and the 95% limits of agreement from ±16.9 to ±13.6 points. Content and construct validity Of the 36 evaluated CPCHILD-DV items, two had a median score of 3 (fairly important), 27 had a median score of 4
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Table 3. Known groups comparison in CPCHILD-scores in motor levels and cognitive levels. GMFCS levels IV n ¼ 29 Personal care/activities of daily living Positioning, transferring and mobility Comfort and emotions Communication and social interaction Health Overall quality of life Total
39.2 39.8 78.1 63.6 67.7 65.3 56.8
V n ¼ 35
(16.0) (10.7) (19.6) (17.7) (22.2) (17.4) (10.7)
28.7 32.7 76.6 46.2 64.1 61.7 47.9
(16.4) (14.7) (21.2) (21.3) (17.8) (16.8) (10.6)
Cognitive levels p Valuea 0.01 0.04 0.76 50.001 0.47 0.39 50.001
I n ¼ 10 34.9 41.7 72.8 72.4 64.7 62.0 55.7
(17.3) (8.4) (22.6) (14.1) (29.7) (17.5) (9.8)
II n¼8 34.7 36.6 79.0 68.2 73.3 77.5 56.8
(17.6) (18.5) (22.1) (22.7) (17.5) (19.8) (14.8)
III n ¼ 24 30.9 33.6 75.4 53.1 71.4 64.3 50.8
(18.1) (11.8) (19.4) (17.3) (18.6) (15.9) (10.8)
IV n ¼ 22 35.5 34.8 82.0 40.6 57.0 60.0 49.2
(16.2) (14.7) (19.6) (18.3) (14.2) (15.1) (11.2)
p Valueb 0.82 0.45 0.59 50.001 0.05 0.09 0.29
All scores are means (SD). GMFCS, Gross Motor Function Classification System: aIndependent sample t-test, bOne-way analysis of variance.
Table 4. Spearman’s rho correlation coefficients between CPCHILD scores and TAPQOL total score. CPCHILD scores
TAPQOL total score
Personal care/activities of daily living Positioning, transferring and mobility Comfort and emotions Communication and social interaction Health Overall quality of life Total
0.09 0.22 0.44a 0.50a 0.39a 0.41a 0.50a
a
Correlation is significant at the 0.01 level (two-tailed).
(very important) and seven had a score of 5 (most important). Table 3 shows the known group validation results. Children in GMFCS level V (poorer motor function) had a significantly lower mean total score on the CPCHILD-DV than those in GMFCS level IV (mean difference 8.9 points (95% CI: 3.6–14.2); p50.001). At domain level there was a statistically significant difference in the domains ‘‘personal care/activities of daily living’’ (10.5 points, 95% CI: 2.4–18.6), ‘‘positioning, transferring and mobility’’ (7.1 points, 95% CI: 0.5–13.6) and ‘‘communication and social interaction’’ (17.4 points, 95% CI: 7.6–27.1). The differences between the four cognitive level groups were only statistically significant in the domain ‘‘communication and social interaction’’ (F: 9.3; df: 3; p50.01). The post-hoc pairwise comparisons (Bonferroni corrected) revealed a statistical significance (p50.01) between the lowest cognitive level IV and each of the two highest levels (II and I, mean difference 27.5 and 31.8 points, respectively). Except for the domains ‘‘personal care/ activities of daily living’’ and ‘‘positioning, transferring and mobility’’, all CPCHILD domain scores (rs from 0.39 to 0.50) and total score (rs ¼ 0.50) were significantly correlated with the TAPQOL (Table 4).
Discussion Our study showed that the CPCHILD is a psychometrically sound proxy-instrument to discriminate between HRQL levels in Dutch non-ambulatory children with CP. The distribution of scores was similar as that observed in the original validation study of the CPCHILD [16]. The internal consistency was high except for one domain, which consists of only 3 items. The test–retest reliability coefficients were in the ‘‘good’’ range, (40.60 [22]) for four domains and the total score and were moderate for two domains (‘‘personal care/activities of daily living’’ and ‘‘positioning, transferring and mobility’’). For the inter-rater reliability, two of the subscales (‘‘positioning, transferring and mobility’’ and ‘‘comfort and emotions’’) and the total score were just above 0.60 and the ICC of ‘‘overall quality of life’’ domain just under
0.60. Although this indicates a ‘‘moderate/good’’ reliability, this result suggests that the CPCHILD-DV, being a proxy instrument, should be preferably administered by the same parent. The measurement error was random with a small systematic error. The original validation study of the CPCHILD showed slightly higher ICCs for the test–retest reliability (ICC total score: 0.85, ICC domains from 0.59 to 0.87) [16]. However, after correction for interpretation errors by some parents (as explained in ‘‘Results, reliability’’), the ICCs were comparable (ICC total score: 0.81, ICC domains from 0.61 to 0.81). This shows that the interpretation errors have a negative impact on the reliability. The occurrence of interpretation errors in this study may be a result of the mode of administration. Questionnaires were sent to the parents to complete at home while in the original study a verbal instruction was provided to the parents. The following results demonstrated the validity of the CPCHILD-DV: there were no floor and ceiling effects, which indicate that this measure is appropriate for the target population and that a good differentiation between the children is possible. Parents rated all items more than sufficiently important, thereby confirming the content validity. As hypothesised, there were significant differences in CPCHILD scores of motor function level (GMFCS) groups. Similar results were found in the original validation study. The differences between the four cognitive levels were – as hypothesised – significant in the domain ‘‘communication and social interaction’’. Convergent validity of the CPCHILD-DV was supported by moderate correlation with the TAPQOL, as was expected. However, the CPCHILD domains ‘‘personal care/activities of daily living’’ and ‘‘positioning, transferring and mobility’’, which were especially developed for non-ambulatory children, had low and insignificant correlations with the TAPQOL total score. This may be the results of the TAPQOL being a generic measure and designed for chronically-ill children in general. The skewed distribution of the TAPQOL scores, for which the TAPQOL is known [21], shows that this measure is not appropriate to discriminate between HRQL levels in non-ambulatory children with CP. In another study, with CP-children the TAPQOL also showed ceiling effects [24]. The results of the convergent validation are fairly similar to those in the original study, in which the total and domain scores were compared with the physical and psychosocial summary scores of the CHQ, a generic measure. The Spearman’s rank correlation in that study ranged from 0.22 to 0.67, 50% was significant and three out of 14 coefficients were 40.50. A limitation of this study was that the generic TAPQOL was the best available measure to evaluate convergence. In the view of the limited variation on the TAPQOL in this specific population, no optimal evaluation of convergent validity was possible. Future studies examining the relation of the CPCHILD scores with other patient variables to further corroborate the instrument’s validity
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are recommended. Furthermore, the instruction for two domains was unclear to some people, and this led to interpretation errors. Editing of the instructions is important and may enhance the reliability. We also decided to add a relevant example to the instruction to avoid errors of interpretation. Because the questionnaires were sent home, with no researcher present, it cannot be guaranteed that the two parents for the same child completed the questionnaires independently. This may have led to an overestimation of the ICCs of the inter-rater reliability. It would have been better to administer the questionnaires at the clinic in separate rooms or in presence of a researcher. However this was, due to practical and organisational reasons, not possible. Instead, we stressed the importance of independent completion to parents as copying each others answers would compromise the study. Another issue is the question whether a proxy-instrument can measure HRQL accurately. This point was also addressed in the original validation study [3]. The best way to measure HRQL is directly from the child, since it has been established that differences can exist in proxy-agreement of child and parent on an individual level [25]. If this is not possible, as is the case in severely disabled children, the next best way (especially at grouplevel) is relying on the perspectives of the parents. In conclusion, this study has shown that the CPCHILD-DV has sufficient reliability and validity as a proxy measure of health status and well-being of non-ambulatory children with CP. Further studies on the sensitivity to change are needed before this instrument can be recommended for use as an outcome measure.
Acknowledgements
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7. 8. 9.
10. 11. 12.
13. 14.
15. 16.
The authors would like to thank the families who participated in this study.
Declaration of interest
17.
The authors report no conflicts of interest.
18.
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