Testing the psychometric properties of 9 bolt-ons for the EQ-5D-5L in a general population sample.

OBJECTIVES: We aim to assess the psychometric performance and added value of nine existing bolt-ons (breathing problems, cognition, hearing, self-confidence, skin irritation, sleep, social relationships, tiredness and vision) for the EQ-5D-5L in a general population sample.

METHODS: The EQ-5D-5L, nine bolt-ons, SF-6Dv1, PROMIS-29+2, PROMIS Global Health and Satisfaction With Life Scale were completed in an online cross-sectional survey among a general adult population sample in Hungary (n=1587). The following psychometric properties were tested for the EQ-5D-5L+bolt-on(s): ceiling, divergent and convergent validity, structural validity, known-group validity and explanatory power.

RESULTS: Adding sleep (30%), tiredness (24%) or vision (21%) substantially reduced the ceiling of the EQ-5D-5L (41%). Cognition, sleep, social relationships and tiredness correlated with corresponding PROMIS and SF-6D items (rs =ǀ0.32ǀ-ǀ0.73ǀ). All bolt-ons, except cognition and self-confidence, loaded on a different factor from the EQ-5D-5L dimensions. Breathing, hearing, skin irritation and vision significantly improved known-group validity in relevant health condition groups. The sleep bolt-on improved known-group validity in 9 out of 13 chronic health conditions. Tiredness had the largest impact on explaining EQ VAS score variance in 8 out of 13 conditions. Hearing and vision improved the ability of the EQ-5D-5L to capture declining health with age, while self-confidence and social relationships were valuable for mental health assessment.

CONCLUSIONS: This study established the validity of multiple bolt-ons for the EQ-5D-5L and highlights the usefulness of including relevant bolt-ons in population-based and patient surveys. Our findings inform the further development of these bolt-ons and the bolt-on item selection for clinical studies.