Detecting DSM-5 somatic symptom disorder: criterion validity of the Patient Health Questionnaire-15 (PHQ-15) and the Somatic Symptom Scale-8 (SSS-8) in combination with the Somatic Symptom Disorder - B Criteria Scale (SSD-12)

Background The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) introduced somatic symptom and related disorders (SSD) to improve the diagnosis of somatoform disorders. It is unclear whether existing questionnaires are useful to identify patients with SSD. Our study investigates the diagnostic accuracy of the Patient Health Questionnaire-15 (PHQ-15) and the Somatic Symptom Scale-8 (SSS-8) in combination with the Somatic Symptom Disorder - B Criteria Scale (SSD-12). Methods For this cross-sectional study, participants were recruited from a psychosomatic outpatient clinic. PHQ-15, SSS-8, and SSD-12 were administered and compared with SSD criteria from a diagnostic interview. Sensitivity and specificity were calculated for optimal individual and combined cutpoints. Receiver operator curves were created and area under the curve (AUC) analyses assessed. Results Data of n = 372 patients [31.2% male, mean age: 39.3 years (s.d. = 13.6)] were analyzed. A total of 56.2% fulfilled the SSD criteria. Diagnostic accuracy was moderate for each questionnaire (PHQ-15: AUC = 0.70; 95% CI = 0.65-0.76; SSS-8: AUC = 0.71; 95% CI = 0.66-0.77; SSD-12: AUC = 0.74; 95% CI = 0.69-0.80). Combining questionnaires improved diagnostic accuracy (PHQ-15 + SSD-12: AUC = 0.77; 95% CI = 0.72-0.82; SSS-8 + SSD-12: AUC = 0.79; 95% CI = 0.74-0.84). Optimal combined cutpoints were > 9 for the PHQ-15 or SSS-8, and > 23 for the SSD-12 (sensitivity and specificity = 69% and 70%). Conclusions The combination of the PHQ-15 or SSS-8 with the SSD-12 provides an easy-to-use and time- and cost-efficient opportunity to identify persons at risk for SSD. If systematically applied in routine care, effective screening and subsequent treatment might help to improve quality of life and reduce health care excess costs.