Item response model validation of the German ICD-11 International Trauma Questionnaire for PTSD and CPTSD

Abstract

Background In the 11th revision of the International Classification of Diseases (ICD-11) posttraumatic stress disorder (PTSD) and the complex variant (CPTSD) were newly conceptualised. The International Trauma Questionnaire (ITQ) was developed as a brief self-report measure to screen for both disorders. The English original version has been rigorously tested and presents convincing psychometric properties. The aim of the current study was to validate the German version by means of item response theory (IRT). Method This is a secondary analysis of a representative, trauma-exposed adult sample from the German general population (N = 500). 1- and 2-parameter logistic IRT models (i.e. examination on an item level), diagnostic rates and confirmatory factor analyses were calculated. Results All items showed good model fit and acceptable to good performance aligning with the items of the English original except for item C1 (Long time to calm down) which had a high endorsement rate and a low discriminatory power yielding low information gain. CPTSD diagnostic rate of 3.2% was lower than in comparable literature. Confirmatory factor analysis deemed the six first-order, two second-order factors model superior. Conclusion Measurement and factorial validity of the German version of the ITQ was confirmed. The German translation matches the English original in most psychometric properties and can thus be used for research and clinical practice.

Epistemic trust and personality functioning mediate the association between adverse childhood experiences and posttraumatic stress disorder and complex posttraumatic stress disorder in adulthood

“…For both scales, reliability was good with α = 0.84 for the PTSD scale and α = 0.88 for the cPTSD scale ( 53 ). The German version has been validated in a representative population-based sample and can be used for research and clinical practice ( 54 ). In our sample, good internal consistency was observed for both the PTSD (α = 0.89) and cPTSD scale (α = 0.87).…”

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

“…The targeting of the six-item PTSD and DSO scales has not previously been investigated. Christen et al ( 2021 ) evaluated item information within the two scales for a representative sample for the German general population; however, it was not related to the distribution of items and persons (i.e. targeting).…”

“…for each grouping variable, item difficulties for each items are equal for the subgroups) across the community and clinical sample, and suggested that there was no substantial issue with lack of invariance. The psychometric findings of Cloitre et al ( 2018 ) concerning dimensionality and invariance for the 12-item ITQ were largely replicated in a German study with nationally representative data, also using dichotomized items (Christen et al, 2021 ). The latter study also found no difference in how well the one- and two-parameter models described the PTSD scale, but as for the community sample in Cloitre et al ( 2018 ), suggested that the two-parameter model described the DSO scale better.…”

“…To our knowledge, only three studies have used IRT methods to study the psychometric properties of the ITQ scales (Christen et al, 2021 ; Cloitre et al, 2018 ; Shevlin, Hyland, Roberts, et al, 2018 ). Cloitre et al ( 2018 ) used a combination of endorsement rates, item discrimination and/or item difficulty, and clinical relevance on 28 dichotomized ITQ items of the extended research version in UK clinical and community samples, to reduce the number of items to six PTSD items and six DSO items.…”

“…The latter study also found no difference in how well the one- and two-parameter models described the PTSD scale, but as for the community sample in Cloitre et al ( 2018 ), suggested that the two-parameter model described the DSO scale better. Furthermore, Christen et al ( 2021 ) called for IRT analyses using the ordinal rather than the dichotomized items in both clinical and community samples, as well as testing for DIF in clinical samples to further understand item functioning. To date, the study by Shevlin, Hyland, Roberts, et al ( 2018 ) is the only IRT study which has analysed the ordinal ITQ items.…”