Rescaling the Post-Traumatic Stress Disorder Checklist for Use in Primary Care

The Posttraumatic Stress Disorder (PTSD) Checklist (PCL) is a 17-item self-report measure of PTSD symptom severity that has demonstrated excellent psychometric properties across a variety of settings, purposes, and populations. The PCL is widely used in busy Department of Defense primary care settings as part of routine PTSD screening, requiring that it is easy for patients to complete and providers to score. The clinical utility of the PCL may be improved through use of a zero-anchored Likert-type response scale by providing intuitive anchors for respondents and fewer calculations for clinic staff; however, changes to the response scale may invalidate the known psychometric properties of the measure. The purpose of this study is to evaluate the equivalence of a zero-anchored PCL to the traditional one-anchored PCL. Differences in total scores were examined using inferential confidence intervals. Substantial overlap of the inferential confidence intervals and small Rg (maximum probable difference) value of 0.68 indicated that the zero-anchored PCL is equivalent to the one-anchored PCL on the basis of our specified delta (amount of difference considered inconsequential). These findings support the use of a zero-anchored PCL in clinical practice, and more broadly, the use of zero-anchored measures in the larger field of psychological assessment.