Purpose: Comparative evidence regarding the responsiveness of the EQ-5D and SF-6D in arthritis patients is conflicting and insufficient across the range of disease severity. We examined the comparative responsiveness of the EQ-5D and SF-6D in cohorts of patients with early inflammatory disease through to severe rheumatoid arthritis (RA).
Methods: Responsiveness was tested using the effect size (ES) and standardised response mean (SRM). Correlation of change in EQ-5D and SF-6D with disease specific measures was tested using Pearson correlations and the Steiger's Z test. Treatment response and self-reported change were used as anchors of important change.
Results: The EQ-5D was more responsive to deterioration (ES ratio (EQ-5D/SF-6D): 1.6-3.0) and the SF-6D more responsive to improvement (ES ratio (SF-6D/EQ-5D): 1.1-1.8) in health. The SF-6D did not respond well to deterioration in patients with established severe RA (ES and SRM 0.08). The EQ-5D provided larger absolute mean change estimates but with greater variance compared to the SF-6D.
Conclusions: The comparative responsiveness of the EQ-5D and SF-6D differs according to the direction of change. The level of mean change of the EQ-5D relative to the SF-6D has implications for cost-effectiveness analysis. Use of the SF-6D in patients with severe progressive disease may be inappropriate.