Psychometric evaluation of the Posttraumatic Stress Disorder Checklist for DSM-5 in daily surveys: An item response theory and longitudinal measurement invariance analysis.

The Posttraumatic Stress Disorder (PTSD) Checklist for the DSM-5 (PCL-5) has demonstrated excellent psychometric qualities across cross-sectional studies, yet the scale's performance in intensive longitudinal studies is less known. Using data from the PCL-5 administered daily for 9 days, we (a) conducted item analysis of the PCL-5 using the graded response model to examine item characteristics (thresholds and discrimination parameters) and (b) examined differential item functioning (DIF) to evaluate whether the PCL-5 measured the PTSD latent trait identically across daily surveys (i.e., longitudinal measurement invariance). Methodologically, 256 trauma-exposed university students (Mage = 21.01 ± 4.24; 85.8 % women; 41.0 % probable PTSD) completed the 20-item PCL-5 for 9 consecutive days. Across days, results indicated lower but acceptable discrimination for PCL-5 items 8 (traumatic amnesia), 16 (reckless or self-destructive behaviors), and 17 (hypervigilance). Further, 14 % of participants exhibited person misfit at least once across the 9 days. DIF analysis indicated that Item 2 (nightmares) exhibited DIF across days indicating potential bias; however, the effect sizes for DIF were negligible. In conclusion, the results broadly provide psychometric support for using the 20-item PCL-5 in intensive longitudinal studies. Future replication of study results across diverse and clinical populations could help to further strengthen these findings.