Comparison of the PTSD Symptom Scale-Interview Version and the Clinician-Administered PTSD scale

The Clinician-Administered PTSD Scale (CAPS) is one of the most frequently used measures of posttraumatic stress disorder (PTSD). It has been shown to be a reliable and valid measure, although its psychometric properties in nonveteran populations are not well known. One problem with the CAPS is its long assessment time. The PTSD Symptom Scale--Interview Version (PSS-I) is an alternative measure of PTSD severity, requiring less assessment time than the CAPS. Preliminary studies indicate that the PSS-I is reliable and valid in civilian trauma survivors. In the present study we compared the psychometric properties of the CAPS and the PSS-I in a sample of 64 civilian trauma survivors with and without PTSD. Participants were administered the CAPS, the PSS-I, and the Structured Clinical Interview for DSM-IV (SCID) by separate interviewers, and their responses were videotaped and rated by independent clinicians. Results indicated that the CAPS and the PSS-I showed high internal consistency, with no differences between the two measures. Interrater reliability was also high for both measures, with the PSS-I yielding a slightly higher coefficient. The CAPS and the PSS-I correlated strongly with each other and with the SCID. Although the CAPS had slightly higher specificity and the PSS-I had slightly higher sensitivity to PTSD, overall the CAPS and the PSS-I performed about equally well. These results suggest that the PSS-I can be used instead of the CAPS in the assessment of PTSD, thus decreasing assessment time without sacrificing reliability or validity.