QLU-C10D Questionnaire: Measurement Properties and Convergent Validity Compared to EQ-5D-5L

This study found that the QLU-C10D questionnaire had well-validated measurement properties. The dimensions of C10D exhibited lower ceiling effects compared to the dimensions of 5L, suggesting that the design of the questionnaire itself contributed to this difference. Furthermore, C10D demonstrated a superior structural breadth when compared to 5L. Interestingly, even patients who were considered to be in good health according to the EQ-5D-5L reported issues when utilizing disease-specific measurements. Specifically, among the 5L respondents, 25 patients selected '1111', whereas only 17 of them chose the same response in C10D (Table 3). Notably, C10D exhibited more problems in the Physical, Social, and Fatigue dimensions. Our findings also diverged from those of Norma B. Bulamu et al.'s study, as we observed disparities in the results generated by the two scales within the Physical dimension, suggesting that the inclusion of mobility, self-care, and usual activities in the Physical dimension of C10D, which are also present in 5L, led to significant content overlap. Consequently, our study's convergent validity results indicated higher correlations between theoretically corresponding domains and an overall strong association between the index scores.