Validation of the MOS SF-36 for quality of life assessment of patients with systemic lupus erythematosus in Singapore

Abstract

Objective. To assess the reliability and construct validity of the Medical Outcomes Study Short Form 36 Health Survey (SF-36) in a multiracial cohort of Asian patients with lupus in Singapore. Methods. A cross sectional study was performed on 118 English speaking patients with lupus attending a specialist rheumatology unit between March and August 1996. Patients completed a questionnaire containing the UK standard version of the SF-36 twice within a 14 day period. All patients were assessed for disease activity using the British Isles Lupus Assessment Group score (BILAG), and for disease related damage using the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index (DI). Relationships between SF-36, BILAG, and DI scores were studied using Spearman's rank correlation. Internal consistency of the SF-36 was assessed using Cronbach's α, and stability using the repeatability coefficient of Bland and Altman. Results. SF-36 subscales showed high internal consistency, with Cronbach's α coefficient ranging from 0.84 to 0.94. Test-retest reliability was acceptable, with Spearman's rank correlation > 0.70 for all subscales except role-physical, and mean differences in test scores of < 2 points for 5 of 8 subscales. SF-36 subscale scores were weakly correlated with BILAG scores (Spearman's p -0.37 to 0.15) and SLICC/ACR DI scores (Spearman's p -0.25 to 0.23), suggesting divergent construct validity of the SF-36. Conclusion. These data suggest the SF-36 is a reliable and valid measure of the quality of life of patients with lupus in Singapore.