Estimating population prevalence of posttraumatic stress disorder: an example using the PTSD checklist.

The PTSD Checklist (PCL) is among the most widely used self-report instruments for assessing PTSD. To determine PCL's performance on a population level, the authors combined data from published studies that compared the PCL with structured diagnostic interviews. Weighted average sensitivities and specificities were calculated for cutoff categories most often reported in the literature. Weighted average sensitivity decreased from .85 to .39 and specificity increased from .73 to .97 for cutoffs ranging from 30 to 60. The PCL's ability to accurately estimate PTSD prevalence varied as a function of cutoff and true PTSD prevalence. In populations with a true PTSD prevalence of 15% or less, cutoff values below 44 will substantially overestimate PTSD prevalence. Uncalibrated use of the PCL for prevalence estimation may lead to large errors.