A comparison of the CAPS-5 and PCL-5 to assess PTSD in military and veteran treatment-seeking samples

Background: This study was an examination of the puzzling finding that people assessed for symptoms of posttraumatic stress disorder (PTSD) consistently score higher on the self-report PTSD Checklist for DSM-5 (PCL-5) than the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5). Both scales purportedly assess PTSD severity with the same number of items, scaling, and scoring range, but differences in scores between measures make outcomes difficult to decipher.

Objective: The purpose of this study was to examine several possible psychometric reasons for the discrepancy in scores between interview and self-report.

Method: Data were combined from four clinical trials to examine the baseline and posttreatment assessments of treatment-seeking active duty military personnel and veterans.

Results: As in previous studies, total scores were higher on the PCL-5 compared to the CAPS-5 at baseline and posttreatment. At baseline, PCL-5 scores were higher on all 20 items, with small to large differences in effect size. At posttreatment, only three items were not significantly different. Distributions of item responses and wording of scale anchors and items were examined as possible explanations of the difference between measures. Participants were more likely to use the full range of responses on the PCL-5 compared to interviewers.

Conclusions: Suggestions for improving the congruence between these two scales are discussed. Administration of interviews by trained assessors can be resource intensive, so it is important that those assessing PTSD severity are afforded confidence in the equivalence of their assessment of PTSD regardless of the assessment method used.

HIGHLIGHTS

• The purpose of this study was to examine two commonly used measures of posttraumatic stress disorder, the Clinician-Administered PTSD Scale (CAPS-5), an interview measure, and the PTSD Checklist (PCL-5), a self-report measure, to explore discrepancies in scores.
• Both measures have the same number of items and range of scores assessing the identical 20 symptoms of PTSD, yet higher scores are reported on the PCL-5.
• It appears that the differences in wording of the anchors may contribute to discrepancies in scoring.
• Addressing these problems would allow for a better match in scoring between scales.