Testing the use of ‘clinical checks’ with the International Trauma Questionnaire to measure PTSD and complex PTSD

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 populations 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 contextualize these results in relation to existing literature on population prevalence estimates derived from clinical interviews and discrepancies between clinical interviews and self-report measures.