Assessing complex PTSD and PTSD: validation of the German version of the International Trauma Interview (ITI)

ABSTRACT

Background: With the introduction of the ICD-11 into clinical practice, the reliable distinction between Posttraumatic Stress Disorder (PTSD) and Complex Posttraumatic Stress Disorder (CPTSD) becomes paramount. The semi-structured clinician-administered International Trauma Interview (ITI) aims to close this gap in clinical and research settings.

Objective: This study investigated the psychometric properties of the German version of the ITI among trauma-exposed clinical samples from Switzerland and Germany.

Method: Participants were 143 civilian and 100 military participants, aged M = 40.3 years, of whom 53.5% were male. Indicators of reliability and validity (latent structure, internal reliability, inter-rater agreement, convergent and discriminant validity) were evaluated. Confirmatory factor analysis (CFA) and partial correlation analysis were conducted separately for civilian and military participants.

Results: Prevalence of PTSD was 30% (civilian) and 33% (military) and prevalence of CPTSD was 53% (civilians) and 21% (military). Satisfactory internal consistency and inter-rater agreement were found. In the military sample, a parsimonious first-order six-factor model was preferred over a second-order two-factor CFA model of ITI PTSD and Disturbances in Self-Organization (DSO). Model fit was excellent among military participants but no solution was supported among civilian participants. Overall, convergent validity was supported by positive correlations of ITI PTSD and DSO with DSM-5 PTSD. Discriminant validity for PTSD symptoms was confirmed among civilians but low in the military sample.

Conclusions: The German ITI has shown potential as a clinician-administered diagnostic tool for assessing ICD-11 PTSD and CPTSD in primary care. However, further exploration of its latent structure and discriminant validity are indicated.

HIGHLIGHTS

• This study validated the German International Trauma Interview (ITI), a semi-structured clinician-administered diagnostic interview for ICD-11 Posttraumatic Stress Disorder and Complex Posttraumatic Stress Disorder.

• Internal reliability, inter-rater agreement, latent structure, and convergent validity were explored in trauma-exposed clinical and military samples from five different in- and outpatient centres in Germany and German-speaking Switzerland.

• The findings supported the German ITI's reliability, inter-rater agreement, convergent validity and usefulness from a patient perspective. Future research should explore its factor structure and discriminant validity, for which differences between the samples were found.

Antecedentes: Con la introducción de la CIE-11 en la práctica clínica, la distinción confiable entre el trastorno de estrés postraumático (TEPT) y el trastorno de estrés postraumático complejo (TEPTC) se vuelve primordial. La Entrevista Internacional de Trauma (ITI por sus siglas en inglés) semiestructurada administrada por un clínico tiene como objetivo cerrar esta brecha en los entornos clínicos y de investigación.

Objetivo: Este estudio investigó las propiedades psicométricas de la versión alemana de la ITI entre muestras clínicas expuestas a traumas de Suiza y Alemania.

Método: Los participantes fueron 143 civiles y 100 militares, edad M = 40.3 años, de los cuales el 53.5% eran hombres. Se evaluaron los indicadores de confiabilidad y validez (estructura latente, confiabilidad interna, acuerdo entre evaluadores, validez convergente y discriminante). El análisis factorial confirmatorio (AFC) y el análisis de correlación parcial se realizaron por separado para los participantes civiles y militares.

Resultados: La prevalencia del TEPT fue del 30% (civiles) y del 33% (militares) y la prevalencia de TEPTC fue del 53% (civiles) y del 21% (militares). Se encontró una consistencia interna y un acuerdo entre evaluadores satisfactoria. En la muestra militar, se prefirió un modelo parsimonioso de primer orden de seis factores a un modelo AFC de segundo orden de dos factores de la ITI TEPT y alteraciones en la autoorganización (AAO). El ajuste del modelo fue excelente entre los participantes militares, pero ninguna solución fue encontrada en los participantes civiles. En general, la validez convergente estuvo respaldada por correlaciones positivas de ITI TEPT y AAO con DSM-5 TEPT. La validez discriminante de los síntomas de TEPT se confirmó entre los civiles, pero fue baja en la muestra militar.

Conclusiones: La ITI alemana ha demostrado un potencial como herramienta de diagnóstico administrada por clínicos para evaluar el TEPT y el TEPTC del CIE-11 en atención primaria. Sin embargo, se requiere una mayor exploración de su estructura latente y su validez discriminante.

KEYWORDS:

• ICD-11
• complex posttraumatic stress disorder
• posttraumatic stress disorder
• diagnostics
• structured clinical interview

PALABRAS CLAVE:

• CIE-11
• trastorno de estrés postraumático complejo
• trastorno de estrés postraumático
• diagnóstico
• entrevista clínica estructurada

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available upon reasonable request. Access to the German Military subsample must be requested from the German Ministry of Defense ([email protected]) while the data collected in civil in- and outpatient centres in Germany and Switzerland are available from the corresponding author.

Additional information

Funding

No funding to report for data collections at Integrierte Psychiatrie Winterthur and Bundeswehr Center for Military Mental Health. Data collection in the other treatment centres in Germany (consultation centres of both Departments of Psychiatry and Neurosciences, Charité – Universitätsmedizin Berlin and the Central Institute of Mental Health Mannheim) was integrated into a larger project focused on the treatment of nightmares in PTSD, which was funded by Bionorica SE, Germany.