"They Don't Give You No Note If It's Got Fentanyl": Using Cognitive Interviews to Understand Self-report and Urine Drug Screen Discrepancies.

Background: Fentanyl, a highly potent synthetic opioid, is now involved in the majority of drug overdose deaths in the United States. Discrepancies between substance use self-reports and urine drug screens (UDS) are common, especially when users are unaware of fentanyl adulteration. Objectives: The objective of this study was to examine the cognitive processes underlying discrepancies between self-reported fentanyl use and UDS results, specifically focusing on participants unaware of their fentanyl exposure. Design: This was a cross-sectional qualitative study. Methods: This study conducted cognitive interviews with 10 participants from a larger clinical trial who tested positive for fentanyl in a UDS but reported no fentanyl use. The interviews explored participants' understanding of survey questions about fentanyl use and their interpretation of UDS results. Responses were analyzed to identify themes related to self-report discrepancies. Results: Participants often underreported fentanyl use, not due to social desirability bias, but because they interpreted survey questions as asking about known, rather than suspected, fentanyl use. Many acknowledged their drugs were likely adulterated but only reported use when they were certain of fentanyl's presence. Conclusion: The findings suggest that refining survey questions to capture both intentional and unintentional fentanyl exposure could improve the accuracy of self-reported data. These adjustments are critical to improve the accuracy of data collected to inform surveillance strategies, effective public health policies, and clinical interventions.