Psychometric Properties of the EuroQol-5D and Short Form-6D in Patients with Systemic Lupus Erythematosus

Abstract

OBJECTIVE: Health related quality of life (HRQOL) is an important patient-reported outcome in systemic lupus erythematosus (SLE). We evaluated the psychometric properties of 2 widely used preference-based generic HRQOL measures, EuroQol-5D (EQ-5D) and Short Form-6D (SF-6D), among United States patients with SLE. METHODS: Patients with SLE enrolled at an academic institution were assessed for self-reported generic HRQOL (EQ-5D, Medical Outcomes Study SF-36), disease activity, and disease damage SF-6D. Physical Component Score (PCS) and Mental Component Score (MCS) were calculated from SF-36. Criterion validity, convergent validity, and known-groups comparisons were evaluated for EQ-5D and SF-6D. Sensitivity to change (t tests, effect size) was evaluated in a subset of the cohort followed longitudinally. RESULTS: One hundred sixty-seven patients with SLE were enrolled. Related domains on the EQ-5D and SF-36 correlated strongly, e.g., mobility and physical functioning (r=0.60), whereas unrelated domains showed weak to moderate correlation. EQ-5D index, EQ-5D visual analog scale, and SF-6D score correlated strongly among each other as well as with most domains of SF-36. Both EQ-5D and SF-6D indices differentiated among patients of varied disease severity. EQ-5D and SF-6D were found to be sensitive to self-reported change in health but insensitive to change in disease activity longitudinally. Disease activity and damage showed weak correlation with HRQOL measures. CONCLUSION: The SF-6D and EQ-5D exhibited satisfactory psychometric properties for use among US patients with SLE. Measures of disease activity and damage were weakly correlated with HRQOL, suggesting that HRQOL is an important complementary source of information about patients with SLE.