The SF-36 summary scores and their relation to mental disorders: physical functioning may affect performance of the summary scores

BACKGROUND AND OBJECTIVES: The Medical Outcomes Study 36-item Short-Form Health Survey (SF-36) has been widely used as a generic measure of health status. It can be scored to provide either a profile of eight scores or two summary measures of health. Several studies demonstrated shortcomings of the summary scores in accurately reflecting patients' physical and mental health on the basis of subscale scores. The objective of this study was to compare and evaluate different scoring algorithms for the summary scores. METHODS: The analysis was based on data on 4,052 respondents from the German National Health Interview and Examination Survey. Mental disorders were assessed using a structured clinical interview. Logistic regression and receiver operating characteristic analyses were used to evaluate the association between the mental component scores and mental disorders. RESULTS: Subjects with mental disorders reported poorer quality of life on all SF-36 subscales and component scores compared to those without mental disorders. The presence of physical disorders resulted in different summary scores. The screening accuracy in detecting subjects with mental disorders was satisfactory for both mental summary scores. CONCLUSIONS: The summary scores should be evaluated in relation to the profile of the eight subscales. Physical functioning should be evaluated carefully when comparing health status using summary scores.