What does 'polysubstance' really mean? Comparing drug-involved deaths in CDC records vs. detailed medical examiner data from Los Angeles

Although concordance is high for single-substance involvement rates, CDC WONDER fails to capture the majority of polysubstance deaths adequately, as about three-quarters of these deaths are incompletely described using its 2-drug limit. This limitation has worsened as deaths increasingly involve more drugs on average. We illustrate a huge variety of polysubstance combinations that can be seen in medical examiner deaths. As the overdose crisis grows increasingly polysubstance in nature, improving the epidemiological tracking of deaths involving multiple drugs, and drugs not captured by ICD-10 codes currently, is of paramount importance.