Substance Use
Using a classification and regression tree output to understand the likelihood of fentanyl presence among people who use drugs in Rhode Island Leah Shaw* Leah Shaw Brandon Marshall Katie Biello Jane Buxton Jacqueline Goldman Scott Hadland Susan Sherman Alexandria Macmadu
Background: The United States is characterized by an unregulated and rapidly changing drug supply. In 2022, approximately 75% of overdose deaths in Rhode Island (RI) involved fentanyl. We sought to characterize sub-populations of people who use drugs (PWUD) at highest risk of fentanyl exposure.
Methods: We utilized baseline data from the Rhode Island Prescription and Illicit Drug Study, a randomized control trial of PWUD from 2020 to 2023. We evaluated sociodemographic and drug use-related covariates from the baseline survey and examined fentanyl presence in urine drug testing (UDT). Our classification and regression tree (CART) analysis highlights subpopulations at the greatest likelihood of fentanyl presence in UDT.
Results: Those with fentanyl present in UDT tended to be younger, non-Hispanic white or Latine, had recently injected drugs, and enrolled during 2022-2023 (N=446; p<0.05 for all). Preference for fentanyl was strongly associated with fentanyl in UDT (p<0.001). The CART analysis demonstrated that participants who suspected fentanyl exposure in their drugs were more likely to have fentanyl present in UDT. Preference for fentanyl also increased the likelihood of fentanyl in UDT, especially in younger participants (see Figure). Participants who were not confident that they had been exposed to fentanyl recently and who had not injected drugs in the past month were unlikely to have fentanyl present in UDT (estimated probability = 0.091). The CART model misclassified 18.31% of observations.
Conclusions: There was substantial variation in the presence of fentanyl in UDT among PWUD in RI and evidence to suggest that PWUD knew if they had recently been exposed to fentanyl. Harm reduction services for people actively injecting drugs and drug checking programs based on capacity building and empowerment targeted towards younger adults and those not yet using other services are urgently needed to support PWUD in navigating the current volatile drug supply.
