Analysis of trends and usage of ICD-10-CM discharge diagnosis codes for poisonings by fentanyl, tramadol, and other synthetic narcotics in emergency department data.

Synthetic opioids, including illicitly manufactured fentanyls, are driving recent increases in US overdose deaths. Beginning October 2020, the International Classification of Diseases, 10th revision, Clinical Modification (ICD-10-CM) code for poisonings involving synthetic narcotics (T40.4X) was split into three codes: fentanyl (T40.41), tramadol (T40.42), and other synthetic narcotics (T40.49). Emergency department data from October 2019-September 2021 in the Centers for Disease Control and Prevention's National Syndromic Surveillance Program BioSense platform were queried for synthetic opioid codes in the chief complaint and discharge diagnosis fields. Trend analyses assessed average monthly percent change overall and by sex and age. Emergency department visits for overdoses involving synthetic narcotics increased on average 3.2 % each month before the code split and 4.8 % after. Visits with fentanyl codes drove this increase after the split, accounting for most visits among males, females, and every age group except ≥ 65 years. The average monthly percent increase for ED visits for fentanyl-involved overdoses was greater than for all synthetic narcotics combined (i.e., T40.41, T40.42, and/or T40.49), suggesting that the old code (T40.4X) masked the full extent of the increase in ED visits for fentanyl overdoses. Usage of these new codes can improve tracking of non-fatal synthetic opioid overdose trends.