The cascade of care for opioid use disorder: a retrospective study in British Columbia, Canada.

BACKGROUND AND AIMS: The 'cascade of care' framework, measuring attrition at various stages of care engagement, has been proposed to guide the public health response to the opioid overdose public health emergency in British Columbia, Canada. We estimated the cascade of care for opioid use disorder and identified factors associated with care engagement for people with opioid use disorder (PWOUD) provincially. DESIGN: Retrospective study using a provincial-level linkage of four health administrative databases. SETTING AND PARTICIPANTS: All PWOUD in BC from 1 January 1996 to 30 November 2017. MEASUREMENTS: The eight-stage cascade of care included diagnosed PWOUD, ever on opioid agonist treatment (OAT), recently on OAT, currently on OAT and retained on OAT: ≥ 1, ≥ 3, ≥ 12 and ≥ 24 months). Health-care use, homelessness and other demographics were obtained from physician billing records, hospitalizations, and drug dispensation records. Receipt of income assistance was indicated by enrollment in Pharmacare Plan C. FINDINGS: A total of 55 470 diagnosed PWOUD were alive at end of follow-up. As of 2017, a majority of the population (n = 39 456; 71%) received OAT during follow-up; however, only 33% (n = 18 519) were currently engaged in treatment and 16% (n = 8960) had been retained for at least 1 year. Compared with those never on OAT, those currently engaged in OAT were more likely to be aged under 45 years [adjusted odds ratio (aOR) = 1.75, 95% confidence interval (CI) = 1.64, 1.89], male (aOR = 1.72, 95% CI = 1.64, 1.82), with concurrent substance use disorders (aOR = 2.56, 95% CI = 2.44, 2.70), hepatitis C virus (HCV) (aOR = 1.22, 95% CI = 1.14, 1.33) and either homeless or receiving income-assistance (aOR = 4.35, 95% CI = 4.17, 4.55). Regular contact with the health-care system-either in out-patient or acute care settings-was common among PWOUD not engaged in OAT, regardless of time since diagnosis or treatment discontinuation. CONCLUSIONS: People with opioid use disorder in British Columbia, Canada show high levels of out-patient care prior to diagnosis. Younger age, male sex, urban residence, lower income level and homelessness appear to be independently associated with increased opioid agonist treatment engagement