Comparative toxicology of syringe exchange and postmortem blood samples in the District of Columbia: Trends and affinity analysis.

This cross-sectional analysis aimed to understand the similarities and differences between drugs detected in syringes collected from syringe service providers in the District of Columbia and fatal overdose deaths captured by the State Unintentional Drug Overdose Reporting System. Substance exposures for these fatal and non-fatal drug use outcomes have not been previously compared. Substance distributions were examined and a paired significance test was used to compare changes over time. Affinity analysis was employed to reveal substance co-occurrences. Between September 2020 and September 2022, 1,118 postmortem blood samples (PBSs) and 3,646 syringes exchange samples (SESs) were processed, with fatal overdoses increasing 24.1%. Polysubstance use was more commonly found in postmortem blood (82.5%) than in syringe samples (48.6%). Of samples containing opioids, 94.8% of blood samples and 86.3% of syringes contained fentanyl, fentanyl analogs or fentanyl precursors/metabolites. PBSs had double the frequency of co-occurring stimulants and opioids (43.9%) as SESs (21.8%). Major changes in occurrence frequency over time were found for opioid and stimulant exposure in both groups, especially in the increased occurrence of fluorofentanyl (>400%), methamphetamine (>90%) and xylazine (>60%), while the incidence of fentanyl, heroin and metabolite morphine declined. These results indicate that while fatal use and syringe exchange populations have distinct substance exposures, which may contribute to differences in mortality rate, their substance distributions have similar change magnitudes. This study highlights the utility of using multiple data sources to provide a comprehensive description of drug use patterns and discusses the limitations in reporting data from each source.