Edinburgh Napier University

  Background: The International Trauma Questionnaire (ITQ) is the most widely used measure of ICD-11 Posttraumatic Stress Disorder (PTSD) and Complex PTSD (CPTSD). This self-report scale has been used to estimate prevalence rates of these disorders in general population and clinical samples but concerns abound that prevalence estimates derived from self-report measures are too high. To address this concern, we previously introduced the concept of adding ‘clinical checks’ to self-report measures to ensure initial responses reflected the intended clinical meaning of the scale item. Here we provide a rationale for adding clinical checks to the ITQ, describe the process of developing them, and demonstrate their effect at the symptom, cluster, and disorder levels in a general population sample.

Methods: A team of researchers and clinicians, including those who developed the ITQ, developed clinical checks for all ITQ items. These were tested using data from a non-probability quota-based representative sample of adults from the United Kingdom (N = 975).

Results: Use of clinical checks led to decreases in symptom endorsements ranging from 18.0% to 43.9%, and symptom cluster requirements from 19.1% to 35.9%. Disorder prevalence estimates without the clinical checks were 5.4% for PTSD and 9.5% for CPTSD. With the clinical checks, prevalence estimates dropped to 3.8% for PTSD (relative decrease = 29.6%) and 4.9% for CPTSD (relative decrease = 48.4%).

Conclusion: Clinical checks can be easily embedded into the ITQ and have a significant effect on prevalence estimates. We contextualise these results in relation to existing literature on population prevalence estimates derived from clinical interviews, and discrepancies between clinical interviews and self-report measures.