The Norwegian version of the PTSD Checklist (PCL): Construct validity in a community sample of 2004 tsunami survivors

Background: The PTSD Checklist (PCL) is a widely used self-administered measure of post-traumatic stress disorder (PTSD) and it has been validated in a variety of languages and cultures. Aim: Evaluate the diagnostic validity of the Norwegian version of a specific PCL (PCL-S) for detecting PTSD in epidemiological research. Methods: Participants were severely exposed Norwegian survivors from the 2004 South-East Asian tsunami. Of 75 individuals asked to participate, 63 responded (84%). PTSD was assessed by PCL-S and the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). These instruments were compared to evaluate the diagnostic validity of the PCL. We used two different scoring methods to diagnose PTSD based on PCL. The first method was based on the dichotomized sum score (cut-off >= 50) and the second was based on the flowchart method following DSM-IV symptom criteria. Area under the curve (AUC), Cohen's kappa, sensitivity and specificity were used to evaluate the agreement between the PCL and SCID-I. Results: According to the clinical interview, 11.3% of the participants met the diagnostic criteria for PTSD. The two scoring methods of PCL-S revealed similar results: according to both methods, 14.5% were categorized with PTSD. AUC was 0.98 (95% CI 0.93-1.00). For Cohen's kappa, the agreement was 0.71. Sensitivity was 0.86 and specificity 0.95. Agreement between PCL and SCID-I investigated for each of the three symptom clusters of PTSD and for the 17 individual items showed mostly a moderate to substantial agreement. Conclusions: The Norwegian version of the PCL-S performed well as a diagnostic instrument for detecting PTSD in epidemiological research.