Development of the psychosomatic symptom scale (PSSS) and assessment of its reliability and validity in general hospital patients in China

To develop and verify the Psychosomatic Symptom Scale (PSSS) among psychosomatic patients and the cut-off value of PSSS in distinguishing psychosomatic patients from health controls. The PSSS was drafted by an expert workgroup. 996 patients and 366 controls from 14 general hospitals in China were recruited to complete PSSS, Patient Health Questionnaire-15 (PHQ-15) and Symptom Checklist-90 (SCL-90). Student's t-test, Kruskal-Wallis test, Cronbach's α, Spearman's correlation, and confirmatory factor analysis (CFA) were used to verify the PSSS. Receiver operating characteristic (ROC) analyses were used to determine the cut-off value. Cronbach α of PSSS was 0.907. The PSSS was significantly correlated with SCL-90 somatization subscale (r = 0.682, P < 0.001) and PHQ-15 (r = 0.724, P < 0.001). CFA supported the theoretical two-factor structure of the PSSS, with comparative fit index (CFI) = 0.979, Tucker-Lewis index (TLI) = 0.977, root mean square error of approximation (RMSEA) = 0.039 (90% CI: 0.035–0.042), and standardized root mean residual (SRMR) = 0.054. As the sum score of PSSS was significantly higher in female, cut-off values were determined as 11 in females and 10 in males respectively. The PSSS is a reliable and valid instrument for measuring psychosomatic symptoms.