The SF-36 Health Survey as a generic outcome measure in clinical trials of patients with osteoarthritis and rheumatoid arthritis: relative validity of scales in relation to clinical measures of arthritis severity
Department of Quantitative Health Sciences
Adult; Analysis of Variance; Arthritis, Rheumatoid; Clinical Trials as Topic; Cross-Sectional Studies; Female; *Health Status Indicators; Humans; Male; Multivariate Analysis; Osteoarthritis; Outcome Assessment (Health Care); Questionnaires; Reproducibility of Results; *Severity of Illness Index; Time Factors
Biostatistics | Epidemiology | Health Services Research
OBJECTIVE: To evaluate the validity of SF-36 Health Survey (SF-36) scale scores and summary measure scores to describe the health burden of arthritis and to be responsive to clinical indicators of arthritis severity used in four clinical trials.
METHODS: Adults participating in four double-blinded, placebo-controlled clinical trials of therapy for osteoarthritis or rheumatoid arthritis were administered the SF-36 concurrent with clinical measures of disease severity (n = 1,016). Data were collected before treatment and 2 weeks after treatment. Mean SF-36 scores for all patients with arthritis at baseline were compared to a sociodemographically equivalent national norm to test the ability of the SF-36 to describe the burden of arthritis. To test the responsiveness of SF-36 scores to clinical measures of arthritis severity, mean SF-36 scale scores were compared across patients differing in arthritis severity before treatment. Two-week mean SF-36 change scores were compared across patients who improved in arthritis severity (responders) versus patients who did not improve (nonresponders). F-statistics and relative validity coefficients were computed to determine how well each SF-36 scale and summary measure discriminated among arthritis severity levels and distinguished treatment responders from nonresponders, relative to the best scale.
RESULTS: Large and statistically significant differences in mean SF-36 scale scores and summary measures were found such that trial participants scored in worse health than a sociodemographically equivalent US general population norm. In addition, the largest SF-36 scale scores were found to significantly differ across clinically defined levels of arthritis severity. Finally, it was found that the SF-36 scales that best discriminate among arthritis severity groups cross-sectionally were also best at discriminating treatment responders from nonresponders.
CONCLUSION: Results of this study support the validity of the SF-36 to document the health burden of arthritis and as a measure of generic health outcome for clinical trials of alternative treatments for osteoarthritis and rheumatoid arthritis patients.
Med Care. 1999 May;37(5 Suppl):MS23-39. Link to article on publisher's site
Kosinski, Mark; Keller, Susan D.; Ware, John E. Jr.; Hatoum, Hind T.; and Kong, Sheldon Xiaodong, "The SF-36 Health Survey as a generic outcome measure in clinical trials of patients with osteoarthritis and rheumatoid arthritis: relative validity of scales in relation to clinical measures of arthritis severity" (1999). Quantitative Health Sciences Publications and Presentations. 566.