Neuropsychological validation of a brief quiz to examine comprehension of consent information in observational studies of substance users

The objective of this study was to determine the accuracy of a brief informed consent quiz (ICQ) to detect consent comprehension in individuals with cognitive impairment (as a proxy of incomprehension) and to explore the degree to which cognitive domains and recent substance use, independently, predict comprehension. We performed a secondary analysis of two cross-sectional studies in individuals with substance use disorders. The ICQ total score was used as the index test and the Montreal Cognitive Assessment (MoCA) as reference standard in receiver operating characteristic curves. Two independent multiple binary logistic regression models were performed using cognitive domains and days of recent substance use as predictors of ICQ outcome. We analyzed data from 215 and 251 participants, respectively. The ICQ showed moderate accuracy for major cognitive impairment (MoCA <= 21) (area under the curve similar to 77) and lower accuracy for mild impairment (MoCA <= 24) (area under the curve similar to 65). Optimal cutoff score was set at 10 points or less for detecting comprehension difficulty. Lower scores in Short-Term Memory, Attention, Language, and Orientation increased the probability of failing the ICQ. A procedure including both the ICQ and cognitive screening measure could improve the accuracy of consent comprehension assessments.