The PedsQLTM 3.0 Neuromuscular Module is a PedsQLTM disease-specific modules designed to measure the neuromuscular specific HRQOL of pediatric patients. It has satisfactory psychometric properties for both the child self-report and the parent proxy-report and is appropriate for children in a broad age range. The data described here support the feasibility, reliability, and validity of the Chinese version of the PedsQLTM 3.0 Neuromuscular Module in children with DMD living in mainland China. To our knowledge, it is also the first time that the PedsQLTM 3.0 Neuromuscular Module was tested on Chinese children with DMD.
There were minimal missing item responses in the Chinese scale, indicating that children and their parents were able to provide good-quality data regarding pediatric HRQOL. However, our results show that there were several items, i.e., “hard to gain or lose weight when one wants to” and “do not have the equipment one needs,” with missing responses. Notably, the percentage of missing values was primarily attributable to 2–7 year old children. The reason may be that younger children had difficulty understand these questions, that most of them could not gain or lose weight, or that they did not require equipments because they were still able to walk. Regardless, this finding is consistent with those of the prior studies with other PedsQLTM disease-specific modules  and indicates that some modifications for items of these subscales are necessary in toddler and young child versions. In addition, the highest ceiling effect was observed in the “About My/My Child’s Neuromuscular Disease” subscale. It is understandable in a mixed participant with different disease severity, where the majority of children with DMD (66.07%) could climb stairs which would be expected to influence markedly their daily lives. There was also a notable floor effect in the “Communication” subscale. It suggests that children with DMD lack good communication; this problem requires the joint efforts of the clinicians and the community.
Internal consistency reliabilities of the Chinese version exceeded the minimum alpha coefficient standard of 0.70 required for group comparisons for all child self-report and parent proxy-report scales. These findings are consistent with reliability estimates for the original English version [11, 12], indicating acceptable reliability of the Chinese version scale. Although Cronbach’s alpha represents the lower limit of reliability of a measurement instrument and is a conservative estimate of actual reliability , scales that did not meet the 0.70 standard should only be used for descriptive analyses. Overall, responses to the Chinese version scale were in the good to excellent agreement range across a 4–6 week period and correlated significantly, supporting test-retest reliability and demonstrating that the Chinese version scale is stable over time.
In order to evaluate the item-subscale correlations of the Chinese version scale, we analyzed Pearson correlations between items and subscale scores. The results of correlations between items and their hypothesized subscales were high, but those between items and other subscales were weak, indicating good scaling success for child self-reports and parent proxy-reports.
Construct validity was assessed with the Known-Groups Method of comparing mobility groups (climb stairs vs. non-climb). The a priori hypothesis that “About My/My Child’s Neuromuscular Disease” subscale would be significantly related to mobility was confirmed for both child self-report and parent proxy-report. The subscales of “Communication” and “About Our Family Resources” showed unqualified discriminate abilities, probably due to the relatively small sample size, and both are recommended for further testing.
Construct validity was further tested by analyzing inter-correlations among the Chinese version scale Scores and the PedsQLTM 4.0 Generic Core Scales and Summary Scores. Consistent with the conceptualization of disease-specific symptoms as causal indicators of generic HRQOL, the majority of inter-correlations among the Chinese version scale and the Generic Core Scales were in the medium to large range, supporting construct validity. Regarding the agreement between child self-report and parent proxy-report of the Chinese version scale, our data were mostly in the moderate agreement range. This is consistent with both the adult and pediatric literature, suggesting that information provided by proxy-respondents is not equivalent to that reported by patients [42, 43]. Imperfect agreement between child self-report and parent proxy-report has been consistently documented in HRQOL measurements of children with and without chronic illness [44, 45], particularly for less observable or internal symptoms.
This study has several limitations that should be considered when interpreting the results. In mainland China, many children with DMD have refused or abandoned treatment for financial reasons, and HRQOL information about these patients is lacking. All of the subjects in this study were recruited in a large city (Chongqing) in mainland China; determining whether the scale can be generalized to other regions will require further studies in other areas. Information on non-participants’ and participants’ socioeconomic status was not available and could affect our findings. The test-retest data were obtained with an interval of around 4–6 weeks, which was considered to be long enough to make the children with DMD and their parents forget their answers from the first test. However, a potential limitation of the long interval was the possibility of the occurrence of positive or negative events affecting the participants. In addition, the small sample size did not allow us to perform a factor analysis; correlation coefficients from factor analyses tend to be less reliable when estimated from small sample sizes . Future studies with larger samples will allow factor analysis with this population. Finally, we did not evaluate the responsiveness, which is used to detect HRQOL changes while a patient’s health status changes over time and can be regarded as additional evidence of instrument validity . Thus, further longitudinal studies are advised to assess responsiveness.