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43. Item Response Theory and Differential Item Functioning in the Prodromal Questionnaire—Brief
Individuals at clinical high risk for psychosis (CHR) experience attenuated psychotic-like experiences, which are traditionally identified using thorough clinical interviews. Without screening, these time-intensive interviews may result in a low hit rate. Thus, several tools, including the Prodromal Questionnaire—Brief (PQ-B), have been created to screen for CHR by assessing for the presence of psychotic-like experiences and associated distress. However, it is unknown if endorsement of psychotic-like experiences and distress varies between demographic groups as assessed by the PQ-B. Differential responding due to group affiliation has the potential of artificially dampening sensitivity and specificity in certain groups. Thus, in this study, we used Item Response Theory (IRT) and Differential Item Functioning (DIF) analyses to determine information provided by each item, and whether the items were differentially predictive between groups. An international sample of 4820 native English speakers provided voluntary demographic information and completed the PQ-B through TestMyBrain.org. IRT analyses revealed that when assessing distress, the denial of an experience provided equal discrimination, but more reliability in comparison to endorsing an experience and denying distress. Additionally, DIF analyses identified several items on the PQ-B that were more often endorsed by older respondents with higher levels of education. Although, the inclusion of distress scores does add a significant amount of unique information beyond the presence of psychotic-like experiences, the use of IRT and DIF analyses indicate that several items on the PQ-B could be changed or removed, and the distress scale could be modified to help improve the sensitivity and specificity of the PQ-B.