Psychometric performance of the CFQ-R-8D compared to the EQ-5D-3L and SF-6D in people with cystic fibrosis

Objective This study aimed to compare the psychometric performance of the Cystic Fibrosis Questionnaire–Revised–8 Dimensions (CFQ-R-8D), a new, condition-specific, preference-based measure, with that of generic preference-based measures EQ-5D-3L and Short Form 6 dimensions (SF-6D). Methods Data from three trials of participants with CF aged ≥ 14 years who completed the CFQ-R and EQ-5D-3L or SF-6D were used. Analyses were undertaken to evaluate convergent validity based on correlations with CFQ-R domain scores. Known-group validity was assessed based on percent predicted forced expiratory volume in one second and pulmonary exacerbations. Responsiveness was based on correlation of change and sensitivity to change based on change in symptom severity. Effect sizes and standardized response means were estimated. Results CFQ-R-8D utilities and dimensions were strongly correlated with most of the overlapping CFQ-R domain scores (ρ > 0.5); EQ-5D-3L and SF-6D utilities and dimensions had moderate (ρ > 0.3) to strong correlations in dimensions capturing similar concepts. All measures showed evidence of known-group validity ( P 0.1) for EQ-5D-3L. The SF-6D had the largest mean change over time and effect sizes, followed by CFQ-R-8D and then EQ-5D-3L. Neither CFQ-R-8D or SF-6D utility scores had ceiling effects (