The construct validity and responsiveness of the EQ-5D-5L, AQL-5D and a bespoke TTO in acute asthmatics

Measuring quality of life in acute asthmatics is challenging, especially when asthma attacks can occur sporadically. Several questionnaires can be used to measure quality of life in this patient group; however, psychometric testing is limited on questionnaires that can be used to estimate Quality Adjusted Life years. The objective of this study is to assess the construct validity (convergent and discriminative validity) and responsiveness of the EuroQol-5-Dimensions 5-Level (EQ-5D-5L), Asthma Quality of Life Utility Index-5 Dimensions (AQL-5D) and Time Trade-Off (TTO) in acute asthma patients.

Data from a prospective cohort study were used to test the validity and responsiveness of the EQ-5D-5L, AQL-5D and TTO in asthma patients who were recruited from UK accident & emergency departments or hospital wards. The spearman's rank correlation coefficient, the Kruskal-Wallis test statistic and the standardized response mean were used to test for convergent validity, discriminative validity and responsiveness, respectively.

One hundred and twenty-one participants were included in the available case analysis. The EQ-5D-5L and AQL-5D showed moderate to strong correlations for convergent validity at baseline, week 4 and week 8. The AQL-5D and TTO showed moderate correlations at week 4 and week 8. No statistical significance was observed for discriminative validity at baseline. Both the EQ-5D-5L and the AQL-5D also showed that they were sensitive to change for the recovery responses.

The EQ-5D-5L and AQL-5D showed stronger construct validity and responsiveness compared to the TTO. Therefore, both the EQ-5D-5L and AQL-5D should be considered for use in future economic evaluations.