Considering unintentional exposure when testing for cocaine use via oral fluid testing.

Research is needed to establish optimal cutoffs to determine cocaine use via oral fluid testing while considering the possibility of unintentional exposure. We compared detection of cocaine and its metabolites to self-reported use while considering other drug use to determine optimal cutoffs to determine intentional use. In this study, 1819 adults entering randomly selected nightclubs were surveyed about cocaine and other drug use and had their oral fluid analyzed using liquid chromatography quadrupole time-of-flight mass spectrometry. We compared self-reported use to detected exposure. 13.6% of participants reported past 24-hour cocaine use, 43.7% tested positive for cocaine exposure (≥1 ng/mL), and 11.8% tested positive for at least one metabolite. 28.6% either tested positive for or reported past 24-hour use of other drugs, primarily ketamine. Among those testing positive for cocaine exposure (n = 794), only 29.1% reported past 24-hour use. Among positive cases, the optimal cocaine concentration cut-point for predicting self-report was ≥ 26 ng/mL. When focusing on the full sample and a subsample with data on past 48-hour reported use, optimal cut-points were ≥ 6 ng/mL and ≥ 5 ng/mL, respectively. However, detection of metabolites was the strongest predictor of self-reported use. Using self-report as the gold standard, metabolite detection most accurately classified reported use, over and above detection of cocaine or other drugs; however, relying solely on detection of metabolites or higher cocaine concentration thresholds often led to under-detection. In conclusion, relying on detection of metabolites or higher concentrations most accurately detects intentional use, but these lack sensitivity to detect a portion of use.