Testing the psychometric characteristics of EQ-5D-5L and respiratory bolt-ons using a sample of the Australian population.

Purpose: The EQ-5D has been used to assess health related quality of life (HRQoL) in respiratory conditions. However, the core descriptive system may not be sensitive to all the HRQoL impacts of these conditions. To increase the sensitivity of the descriptive system, two respiratory specific bolt-ons, have been developed. Psychometric assessment of the bolt-ons in comparison to other validated instruments is required to facilitate their use. Therefore, the aim of this study is to test the psychometric characteristics of the EQ-5D-5L + R using a large dataset collected in Australia.

Methods: A cross-sectional online survey was used to recruit adult respondents (≥ 18 years) representative of the Australian population. Descriptive and psychometric analyses were used to understand the performance of the EQ-5D-5L and bolt-ons in comparison to other validated instruments. The construct validity was estimated using correlations. Known-group validity was tested to determine the sensitivity of the instruments to differences across different severity groups.

Results: Overall 10,033 respondents (52% female) completed the survey, of which 300 had a respiratory condition. There were moderate to high correlation between bolt-ons with EQ-5D-5L and WHODAS. The EQ-5D-5L + bolt-ons slightly reduced the ceiling effect in comparison to the EQ-5D-5L. The effect size was larger for people with respiratory conditions than people who did not have a respiratory condition.

Conclusion: The results show that adding the respiratory bolt-on to the EQ-5D-5L might slightly improve the instruments descriptive sensitivity. The choice of bolt-on may be driven by whether overall problems or limitations are being measured.