The eight item Somatic Symptom Scale (SSS-8) was recently developed as a brief, patient-reported outcome measure of somatic symptom burden. The scale assesses common somatic symptoms and is a shortened version of the PHQ-15 questionnaire scale, it was first developed for the DSM 5 field trials that investigated the newly established somatic symptom disorder (Zijlema, 2013). The SSS-8 has a five point response option instead of the three point options for the PHQ-15, and a seven day time frame instead of the four week time-frame for the PHQ-15 Initially called the PHQ-SSS in the DSM 5 field trials it was renamed to shorten it and reflect the number of items (Gierk et al., 2015).
Psychometric properties
Research found the SSS-8 was a reliable and valid measure of somatic symptoms and cut-off scores identify individuals with low, medium, high, and very high somatic symptom burden.
One survey study (n = 2510), identified the SSS-8 to have excellent item characteristics and good reliability (Cronbach α = 0.81). 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 (Gierk et al., 2014).
Gierk et al., 2015 did a comparison study between the SSS-8 and the PHQ-15 with psychosomatic outpatients (n=131) and found the reliabilities of the PHQ-15 and SSS-8 were α=0.80 and α=0.76, respectively and both scales were highly correlated (r=0.83). The item characteristics were comparable. There was the same pattern of correlations with measures of depression, anxiety, health anxiety and health-related quality of life (r=0.32 to 0.61). On both scales a 1-point increase was associated with a 3% increase in health care use. The percentile distributions of both scales were similar.
References
Gierk, B., Kohlmann, S., Kroenke, K., Spangenberg, L., Zenger, M., Brähler, E., & Löwe, B. (2014). The somatic symptom scale–8 (SSS-8): a brief measure of somatic symptom burden. JAMA internal medicine, 174(3), 399-407.
Gierk, B., Kohlmann, S., Toussaint, A., Wahl, I., Brünahl, C. A., Murray, A. M., & Löwe, B. (2015). Assessing somatic symptom burden: A psychometric comparison of the Patient Health Questionnaire—15 (PHQ-15) and the Somatic Symptom Scale—8 (SSS-8). Journal of psychosomatic research, 78(4), 352-355.
Zijlema, W. L., Stolk, R. P., Löwe, B., Rief, W., White, P. D., & Rosmalen, J. G. (2013). How to assess common somatic symptoms in large-scale studies: a systematic review of questionnaires. Journal of psychosomatic research, 74(6), 459-468.