Validation of the Danish International Trauma Questionnaire for posttraumatic stress disorder in chronic pain patients using clinician-rated diagnostic interviews.

Background: The estimated prevalence rate of comorbid posttraumatic stress disorder (PTSD) is high in trauma-exposed chronic pain patients. At the same time, self-report measures of PTSD tend to be over-inclusive within this specific population due to the high symptom overlap resulting in potential false positives. There is a need for an updated PTSD screening tools with a proper validation against clinical interviews according to the recently published 11th revision of the World Health Organization's International Classification of Diseases (ICD-11). Objective: The present study aimed to validate the Danish International Trauma Questionnaire (ITQ) PTSD part in a sample of trauma-exposed chronic pain patients. Method: The ITQ was validated using a clinician-rated diagnostic interview of ICD-11 PTSD among chronic pain patients exposed to accident or work-related trauma (N = 40). Construct validity, concurrent and discriminant validity was investigated using confirmatory factor analyses (CFA) and correlation analysis, respectively. Three CFA models of ITQ PTSD part were tested in a sample of trauma-exposed chronic pain patients (N = 1,017) and a subsample of chronic pain patients exposed to accident or work-related trauma only (n = 367). Results: Diagnostic consistency between the six ICD-11 PTSD symptoms derived from the ITQ and the clinical interview (κ = .59) and the overall accuracy of the scale (AUC = .90) were good. The Danish ITQ showed excellent construct, concurrent and discriminant validity. The ICD-11 three factor PTSD model had excellent fit in both the full sample and the subsample of traffic and work-related accidents. Conclusions: The results indicate that the ITQ also has good psychometric properties in patients with chronic pain.