Assessing PTSD in the military: Validation of a scale distributed to Danish soldiers after deployment since 1998

Since 1998, soldiers deployed to war zones with the Danish Defense (≈31,000) have been invited to fill out a questionnaire on post‐mission reactions. This provides a unique data source for studying the psychological toll of war. Here, we validate a measure of PTSD ‐symptoms from the questionnaire. Soldiers from two cohorts deployed to Afghanistan with the International Security Assistance Force ( ISAF ) in 2009 ( ISAF 7, N = 334) and 2013 ( ISAF 15, N = 278) filled out a standard questionnaire (Psychological Reactions following International Missions, PRIM ) concerning a range of post‐deployment reactions including symptoms of PTSD ( PRIM ‐ PTSD ). They also filled out a validated measure of PTSD ‐symptoms in DSM ‐ IV , the PTSD ‐checklist ( PCL ). We tested reliability of PRIM ‐ PTSD by estimating Cronbach's alpha, and tested validity by correlating items, clusters, and overall scale with corresponding items in the PCL . Furthermore, we conducted two confirmatory factor analytic models to test the factor structure of PRIM ‐ PTSD , and tested measurement invariance of the selected model. Finally, we established a screening and a clinical cutoff score by application of ROC analysis. We found high internal consistency of the PRIM ‐ PTSD (Cronbach's alpha = 0.88; both cohorts), strong item‐item (0.48–0.83), item‐cluster (0.43–0.72), cluster‐cluster (0.71–0.82) and full‐scale (0.86–0.88) correlations between PRIM ‐ PTSD and PCL . The factor analyses showed adequate fit of a one‐factor model, which was also found to display strong measurement invariance across cohorts. ROC curve analysis established cutoff scores for screening (sensitivity = 1, specificity = 0.93) and clinical use (sensitivity = 0.71, specificity = 0.98). In conclusion, we find that PRIM ‐ PTSD is a valid measure for assessing PTSD ‐symptoms in Danish soldiers following deployment.