Theme: Epidemiology & Public Health Research Year: 2024
Background: Health administrative data can support population-level research among people who inject drugs, however these data sources remain underutilized due to the difficulty in identifying drug use (IDU) in routinely collected data. We validated case-ascertainment algorithms to identify IDU and tested their application in identifying people who inject drugs among all those diagnosed with hepatitis C (HCV) provincially in Ontario, Canada.
Methods: We linked reference standard cohorts of people who inject drugs (injected within the past 12 months) recruited via community-based studies and matched population controls to health administrative data in Ontario, Canada (1992-2020). We validated case-ascertainment algorithms including combinations of codes for hospitalizations/emergency department (ED) visits for drug use/poisoning, physician visits for drug use, opioid agonist treatment (OAT), or injecting-related infections. We estimated sensitivity and specificity of algorithms for injecting history (any indication 1992+) or recent injecting (past 1-5 years). We then applied a high performing algorithm among all Ontarians with a laboratory-confirmed HCV diagnosis between 1999-2018, alive up to December 31, 2018, to identify a sub-cohort of people who inject drugs with HCV.
Results: An algorithm including ≥1 hospitalization/ED visit or ≥1 physician visit for drug use or ≥1 OAT record had high accuracy for identifying IDU history (91.6% sensitivity, 94.2% specificity) and recent IDU (using 3 years lookback: 80.4% sensitivity, 99% specificity). When applied to a provincial cohort of 112,947 Ontarians diagnosed with HCV, this algorithm estimated 46% (N=52,248) had a history of IDU, of whom 52% (N=27,246) had an indication of recent IDU (within the past 3 years).
Conclusion: The methods developed in this study can enhance the capacity of population-level health research among people who inject drugs and support applied public health interventions towards hepatitis C elimination.
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