Identification of Sum Score Cutoffs for Posttraumatic Stress Disorder in Military Personnel Using the International Trauma Questionnaire (ITQ): A Receiver Operating Characteristic (ROC) Analysis.

Military populations are at elevated risk for developing posttraumatic stress disorder (PTSD). The International Trauma Questionnaire (ITQ) is a self-report instrument that allows for the assessment of PTSD and presents opportunities for wider use as a screener for both clinical and epidemiological purposes. However, current scoring methods are limited, and no cumulative sum score cutoffs have been validated at this time. This study aimed to establish PTSD cutoff scores for the ITQ with a large sample of Norwegian military veterans (N = 5640), 182 of whom met criteria for probable PTSD based on recommended cutoffs for the PTSD Checklist for DSM-5 (PCL-5). By comparing the PTSD subscale of the ITQ to recommended cutoffs for the PCL-5, this study provides the field with a data-driven bridge and calibration between two of the most prominent self-report PTSD instruments available. Results of receiver operating characteristic (ROC) analysis yielded two cutoff values. A score of 6 using the six PTSD symptom items of the ITQ identified probable PTSD cases with the highest sensitivity and minimal false positives and was thus the recommended cutoff for clinical screening purposes. Meanwhile, a score of 7 with these six symptom items yielded the highest confidence that positive results reflected probable PTSD cases and reduced false positives even further at the cost of losing some sensitivity, and it was therefore the recommended cutoff for research purposes. Findings indicate these cutoff values can be used to screen for probable cases of PTSD across both clinical and research contexts but, like those of the PCL-5, must be interpreted cautiously given the limitations of self-report screeners for psychiatric diagnosis.