The Questionnaire for Psychotic Experiences (QPE), a 50-item instrument that measures various psychotic phenomenon, offers a high level of reliability and validity for use in clinical and research settings. This is according to a study published in Schizophrenia Bulletin.
An International Consortium on Hallucination Research working group comprised of experts from psychology, psychiatry, and neurology convened with consumer representatives to develop and evaluate the reliability and validity of the QPE. Investigators examined the ability of the QPE to assess hallucinations (ie, auditory, visual, olfactory, tactile, and multimodal hallucinations and sensed presence) and delusions (ie, paranoid, reference, guilt, control, religious, grandeur, somatic, Cotard’s syndrome, and Capgras syndrome). Participants with schizophrenia (n=50), schizoaffective disorder (n=26), bipolar affective disorder (n=31), and major depressive disorder (n=34), and those without a need for care (ie, nonclinical participants [n=32]), completed the questionnaire during a semistructured interview.
Each participant reached the end of the QPE interview, demonstrating the questionnaire’s high acceptability. A total of 19 of 84 correlations demonstrated significant correlations at P <.0001, demonstrating convergent validity. All the 19 correlations except 1 were significant, whereas the other 65 correlations were not significant. None of the 32 correlations made to test discriminant validity demonstrated significant correlation at P <.0001. For reliability, the intraclass correlation coefficients for stability were between 0.70 and 0.92, and for equivalence they were between 0.99 and 1.00.
The modest size of the sample, the focus on symptoms rather than diagnoses, and the recruitment of only a psychiatric sample represent limitations of the study.
“The QPE fulfils a need that the research and clinical communities have for a transdiagnostic assessment of psychotic experiences,” the researchers explained. “In addition, the QPE could be used as an outcome measure for intervention research.”
Rossell SL, Schutte MJL, Toh WL, et al. The questionnaire for psychotic experiences: an examination of the validity and reliability. Schizophr Bull. 2019;45(suppl 1):S78-S87.