Cross-cultural validity and psychometric properties of the International Trauma Questionnaire in a clinical refugee sample

Background: The ICD-11 post-traumatic stress disorder (PTSD) and complex PTSD diagnoses have been examined in several studies using the International Trauma Questionnaire (ITQ). The cross-cultural validity of the ITQ has not previously been studied using item responses theory methods focused on the issue of equal item functioning and thus comparability of scores across language groups. Objective: To investigate the cross-cultural validity of the ITQ scales considering specifically local independence of items and differential item functioning (DIF) in a cross-cultural sample of refugees. Method: Data from 490 treatment-seeking refugees were included, covering Danish, Arabic, and Bosnian languages and different levels of interpreter-assisted administration. Rasch and graphical log-linear Rasch models were used. Results: There was strong local dependence among items from the same symptom clusters in the PTSD and disorders in self-organization (DSO) scales, except between affective dysregulation items. Weak local dependence was discovered between an item from the affective dysregulation cluster and an item from the disturbed relationship cluster. There was no evidence of DIF related to language or interpreter assistance. There was evidence of DIF for two PTSD items relative to gender and time since the traumatic event. The targeting of the scales to the study population was not optimal. Reliability varied from 0.55 to 0.78 for subgroups. Conclusions: The PTSD and the DSO scales have stable psychometric properties across the Danish, Arabic, and Bosnian language versions and different levels of assisted administration. Scores are comparable across these groups. However, DIF relative to gender and time since trauma introduces considerable measurement bias. DIF-adjusted summed scale scores or estimated person parameters should be used to avoid measurement bias. Future research should investigate whether scales including more and/or alternative items that require higher levels of PTSD and DSO to be endorsed will improve targeting and measurement precision for refugee populations.