Short communicationLiteral text analysis of poly-class and polydrug overdose deaths in North Carolina, 2015–2019
Introduction
Drug overdose mortality continues to climb in the United States (U.S.), with a national rate that has more than tripled over the past two decades (Hedegaard et al., 2020). Recent surveillance demonstrates that stimulant and polysubstance involvement in overdose deaths is increasing (Hedegaard et al., 2021, Kariisa et al., 2019), such that an estimated two-thirds of opioid-related deaths in 2017–2018 involved stimulants or benzodiazepines (Gladden et al., 2019). These shifting patterns of drug involvement underscore the need for comprehensive surveillance of overdose fatalities to inform prevention and substance use disorder treatment efforts.
Research evaluating drug involvement in overdose fatalities has frequently used National Vital Statistics System—Mortality data (Jones et al., 2018, Mattson et al., 2021, Rudd et al., 2014), which is coded with the International Classification of Disease, 10th revision (ICD-10) system to categorize underlying and multiple causes of death (Bramer, 1988). While the utility of ICD-10 codes is inherent in their standardization, research using these codes is limited by a lack of specificity, as they primarily reflect broad categorizations of substances. For example, overdose deaths involving fentanyl and buprenorphine are indistinguishable because these drugs are both classified under one ICD-10 code (T40.4—synthetic narcotics). Thus, relying on ICD-10 codes results in an inability to examine specific drugs.
The literal cause-of-death text is the descriptive information provided by the medical certifier of the death certificate, offering richer details than ICD-10 codes on the circumstances causing and contributing to death (National Center for Health Statistics, 2003). Given its unstructured format, literal text is infrequently used for research; however, it can enhance surveillance of overdose deaths and enable the monitoring of specific drug involvement (Golladay et al., 2020, Hedegaard et al., 2019, Trinidad et al., 2016, Warner et al., 2016). Accordingly, the purpose of this analysis was to leverage the literal text on death certificates to 1) conduct an in-depth examination of trends in the specific drugs and combinations involved in NC overdose deaths from 2015 to 2019, 2) understand the extent of information gleaned from literal text versus ICD-10 codes, and 3) develop a straightforward statistical program that can be integrated into overdose surveillance across states and jurisdictions.
Section snippets
Data source & study population
This descriptive analysis utilized 2015–2019 death certificate data for deaths occurring in NC among NC residents, which contain underlying and multiple cause-of-death ICD-10 codes and literal text. In NC, all suspected drug overdose deaths are investigated by the NC Office of the Chief Medical Examiner, which implemented a statewide process in the late 2000s to standardize assessment and reporting procedures for suspected overdose fatalities, including toxicology assays that screen for >600
Results
Poly-class involvement in overdose deaths in NC increased from 2015 to 2019 (Fig. 1). Based on ICD-10 T-codes, 58% of overdose deaths in 2015 involved multiple substances, increasing to 65% in 2019. Based on the literal text, 64% of overdose deaths in 2015 involved multiple substances, which increased to 67% by 2019. The literal text also indicated that ~75% of overdose deaths had polydrug involvement in 2017–2019, with an average of 2.4 (range: 0–9) drug mentions per death in 2019.
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Discussion
This literal text analysis demonstrated that poly-class overdose deaths in NC increased from 2015 to 2019, corroborating previous research utilizing ICD-10 codes (Figgatt et al., 2021) and findings from other states (Golladay et al., 2020, Schneider et al., 2021). Literal text consistently identified a greater percentage of overdose deaths with poly-class involvement compared to ICD-10 T-codes and provided further specificity that approximately 3 in 4 overdose deaths had polydrug involvement.
Conclusions
Existing research using national death certificate data has established regional differences in drug involvement in overdose deaths (Hedegaard et al., 2019, Kariisa et al., 2019), highlighting the importance of comprehensive, state-level research. To our knowledge, this is one of the first examinations of specific drugs and polydrug combinations using statewide literal text data. Development of the statistical program (https://doi.org/10.17615/9yrd-cr03) allows for incorporation of literal text
Role of funding source
This work was supported by an award from the National Center for Injury Prevention and Control in the CDC) to the North Carolina Division of Public Health (Overdose Data to Action, cooperative agreement #5NU17CE925024-02-00); authors from the University of North Carolina at Chapel Hill were funded through a subcontract under this grant (contract # 5118396).
CRediT authorship contribution statement
KYS, AEA, RBN conceptualized and designed the study. KYS conducted all statistical analyses and prepared the first draft of the manuscript. All authors critically reviewed the manuscript and provided input. KYS, AEA, RBN contributed to manuscript revisions. All authors have reviewed and approved the final manuscript.
Declaration of Competing Interest
No conflict declared.
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