Psychometric Evaluation of the Dutch International Trauma Questionnaire for the 11th Revision of the International Classification of Diseases Posttraumatic Stress Disorder and Complex Posttraumatic Stress Disorder

Background: The International Trauma Questionnaire (ITQ) is a recent self-report measure to assess the severity and probable posttraumatic stress disorder (PTSD) and complex PTSD (CPTSD) as defined by the 11th revision of the International Classification of Diseases. Few studies have examined the psychometric properties of full and short ITQ versions in depth. Therefore, we aimed to evaluate the psychometric properties of the Dutch-translated 28-item ITQ and the 12-item version. Method: Data were used from existing clinical studies and routine clinical assessments for the 28-item (n = 956) and 12-item (N = 4,944) ITQ versions in trauma-exposed treatment-seeking individuals in the Netherlands. Internal consistency and factor validity were assessed, and rates of probable PTSD and CPTSD were estimated. In addition, convergent and discriminant validity were examined by correlations with similar and dissimilar measures. Results: Both versions of the ITQ showed good internal consistency and convergent validity. Confirmatory factor analysis showed that both a first-order correlated six-factor model and a two-factor second-order model were a good representation of the latent structure for the ITQ-12. The ITQ-12 resulted in higher CPTSD rates compared to the ITQ-28 (47% vs. 36.3%), while a similar number of patients met the criteria for either PTSD or CPTSD (70.6% vs. 76.4%). Conclusion: Internal consistency and convergent validity for the ITQ-12 and ITQ-28 were supported. The factorial validity was good for the ITQ-12 and acceptable for the ITQ-28. The discrepancy in CPTSD rates between the ITQ-12 and ITQ-28 calls for further testing of scoring methods against diagnostic clinical interviews for CPTSD. Clinical Impact Statement The psychometric properties of the Dutch International Trauma Questionnaire (ITQ) were supported in a clinical sample. Results support the use of the ITQ as an instrument to assess the symptom severity of the 11th revision of the International Classification of Diseases posttraumatic stress disorder and complex posttraumatic stress disorder. However, there is a need to investigate the accuracy with which the self-report ITQ assesses the two disorders by comparison with clinician-administered interviews.