Reliability and validity of the Depression and Somatic Symptoms Scale among patients with chronic low back pain

BACKGROUND: The Depression and Somatic Symptoms Scale (DSSS), which is a free scale that includes a depression subscale (DS) and a somatic subscale (SS), was developed to evaluate depression and somatic symptoms simultaneously. This study aimed to examine the reliability and validity of the DSSS among patients with chronic low back pain (CLBP). METHODS: Two-hundred and twenty-five patients with CLBP were enrolled. Psychiatric diagnoses were made based on the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders-IV-Text Revision. The DSSS, Oswestry Disability Index, Hospital Anxiety and Depression Scale (HADS), and Short Form 36 (SF-36) were administered. Cronbach’s alpha was used to test internal consistency. Receiver operating characteristic (ROC) analysis was used to identify cutoff scores for a major depressive episode (MDE). RESULTS: Subjects with an MDE (N=21) had greater severities of depression, anxiety, somatic symptoms, and disability as compared with those without an MDE. The Cronbach’s alpha values of the DS and SS were 0.90 and 0.83, respectively. The DS and SS were significantly correlated with the Oswestry Disability Index, the HADS, and the SF-36 subscales. The DS had the greatest area under the receiver operating characteristic curve (0.96) as compared with the SS and the HADS subscales. The cutoff score for an MDE was a DS score ≥15 (sensitivity and specificity: 100% and 88.7%, respectively). CONCLUSION: The DSSS subscales were of acceptable reliability and validity. The DS can be used as a tool for evaluating the severity of depression and detecting an MDE in patients with CLBP.