Benjamin Gierk1, Sebastian Kohlmann1, Kurt Kroenke2, Lena Spangenberg3, Markus Zenger3, Elmar Brähler3, Bernd Löwe1. 1. Department of Psychosomatic Medicine and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany2Schön Clinic Hamburg Eilbek, Hamburg, Germany. 2. Department of Medicine, Indiana University, Indianapolis4Veterans Affairs Health Services Research and Development Service, Center for Health Information and Communication, Indianapolis, Indiana5Regenstrief Institute, Inc, Indianapolis, Indiana. 3. Department of Medical Psychology and Medical Sociology, University of Leipzig, Leipzig, Germany.
Abstract
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 α, 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 α = 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 0.60]), 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.
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 α, 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 α = 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 0.60]), 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.
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