The Somatic Symptom Scale-8 (SSS-8) A Brief Measure of Somatic Symptom Burden

IMPORTANCE Somatic symptoms are the core features of many medical diseases, and they are used to evaluate the severity and course of illness. The 8-item Somatic Symptom Scale (SSS-8) was recently developed as a brief, patient-reported outcome measure of somatic symptom burden, but its reliability, validity, and usefulness have not yet been tested. OBJECTIVE To investigate the reliability, validity, and severity categories as well as the reference scores of the SSS-8. DESIGN, SETTING, AND PARTICIPANTS A national, representative general-population survey was performed between June 15, 2012, and July 15, 2012, in Germany, including 2510 individuals older than 13 years. MAIN OUTCOMES AND MEASURES The SSS-8 mean (SD), item-total correlations, Cronbach alpha, factor structure, associations with measures of construct validity (Patient Health Questionnaire-2 depression scale, Generalized Anxiety Disorder-2 scale, visual analog scale for general health status, 12-month health care use), severity categories, and percentile rank reference scores. RESULTS The SSS-8 had excellent item characteristics and good reliability (Cronbach alpha = 0.81). The factor structure reflects gastrointestinal, pain, fatigue, and cardiopulmonary aspects of the general somatic symptom burden. Somatic symptom burden as measured by the SSS-8 was significantly associated with depression (r = 0.57 [95% CI, 0.54 to 0.601), anxiety (r = 0.55 [95% CI, 0.52 to 0.58]), general health status (r = -0.24 [95% CI, -0.28 to -0.20]), and health care use (incidence rate ratio, 1.12 [95% CI, 1.10 to 1.14]). The SSS-8 severity categories were calculated in accordance with percentile ranks: no to minimal (0-3 points), low (4-7 points), medium (8-11 points), high (12-15 points), and very high (16-32 points) somatic symptom burden. For every SSS-8 severity category increase, there was a 53% (95% CI, 44% to 63%) increase in health care visits. CONCLUSIONS AND RELEVANCE The SSS-8 is a reliable and valid self-report measure of somatic symptom burden. Cutoff scores identify individuals with low, medium, high, and very high somatic symptom burden.