Linking Biomarkers to Lived Use: Concordance Between Serum and Urine Drug Biomarker Concentrations and Self-Reported Opioid Use Among a Prospective Cohort of Individuals Using Opioids in San Francisco John Halifax, MS • Graduate Student Researcher • Division of Epidemiology • UC Berkeley School of Public Health In this upcoming talk, John Halifax will present findings from the San Francisco General Hospital Opioid Treatment Outpatient Program’s (OTOP) toxicology monitoring program and the OCTUPUS (Optimizing Comprehensive drug Testing for Overdose Prevention Using Substance use biomarkers) study of reported “iso” use in San Francisco. In early 2023, patients at SFGH began reporting use of “tranq” and “iso,” thought to refer to fentanyl mixed with xylazine and the synthetic opioid isotonitazene, respectively. In response, OTOP launched urine toxicology monitoring in March 2023 to provide timely data to patients, clinicians, and public health leaders. The OCTUPUS study further surveyed a subset of OTOP intake patients about recent substance use and linked their reports with expanded toxicology testing. This talk will review findings from OTOP monitoring and examine OCTUPUS data to clarify the meaning and clinical significance of reported “iso” use. John Halifax is an Epidemiology PhD student at UC Berkeley’s School of Public Health. He broadly explores the role of neighborhood and place as determinants of health from an ecosocial perspective using flexible, minimally assumptive causal inference methods. His current research includes extending causal inference methods to account for neighborhood-specific confounding effects in multilevel, high-dimensional data settings, examining the effect of acute community violence on perinatal outcomes, and utilizing machine learning to forecast fatal overdoses at the neighborhood level. Prior to pursuing a PhD, John worked at the intersection of analytical chemistry, community health, and the overdose crisis at San Francisco AIDS Foundation and UC San Francisco. John holds an MS in Epidemiology from UC Berkeley and a BS in Chemistry magna cum laude from Haverford College. Outside of work, you will find John riding his bicycle, cooking heirloom beans, or watching his favorite soccer team lose again. --------------------------------- The UCSF Drug Use Research Group (DURG) is a city-wide seminar attended by faculty, postdoctoral fellows, graduate students, and other Bay Area investigators centering on persons who use drugs. The DURG was founded in 2005 after a friendly debate between an epidemiologist and anthropologist on the merits of quantitative versus qualitative research methods. These monthly meetings provide a community platform for new and established investigators to present their works-in-progress, consult on new or related research and policy questions, and prepare for grant applications, conferences, and publications in a supportive environment. The seminar has been successful in cultivating new research collaborations, mentorship, and sustaining interdisciplinary and interprofessional dialogue between those engaged in basic sciences, epidemiology, clinical research, and qualitative methods. Our meetings are not recorded or live-streamed. If you would like to attend the seminar or present your work for dissemination, collaboration, and/or peer review, please contact Leslie Suen, MD, MAS: Leslie.Suen@ucsf.edu