Hazard ratios for associations between incident hepatitis C virus infection and prescribed dosage of opioid agonist treatment, categorized according to tertiles* and patient-perceived dosage adequacy
| Dosage of opioid agonist treatment and perceived adequacy | No. of observations | No. of person-years of follow-up | No. of incident cases | Rate per 100 person-years | Unadjusted HR (95% CI) | Adjusted HR† (95% CI) |
|---|---|---|---|---|---|---|
| Not enrolled in opioid agonist treatment | 1831 | 782.78 | 118 | 15.07 | 1.00 (Ref.) | 1.00 (Ref.) |
| High dosage, perceived adequate | 390 | 167.10 | 4 | 2.39 | 0.18 (0.07–0.50) | 0.27 (0.10–0.74) |
| High dosage, perceived inadequate | 113 | 49.90 | 2 | 4.01 | 0.32 (0.08–1.28) | 0.37 (0.09–1.49) |
| Moderate dosage, perceived adequate | 402 | 156.06 | 12 | 7.69 | 0.59 (0.32–1.07) | 0.93 (0.50–1.72) |
| Moderate dosage, perceived inadequate | 139 | 49.28 | 6 | 12.18 | 0.83 (0.37–1.89) | 1.40 (0.61–3.24) |
| Low dosage, perceived adequate | 381 | 158.05 | 14 | 8.86 | 0.75 (0.43–1.31) | 1.21 (0.68–2.14) |
| Low dosage, perceived inadequate | 173 | 59.41 | 12 | 20.20 | 1.42 (0.78–2.58) | 1.95 (1.06–3.59) |
Note: CI = confidence interval, HR = hazard ratio, Ref. = reference category.
↵* Prescribed dosage was categorized as high if methadone > 80 mg/d or if buprenorphine > 14 mg/d; moderate if methadone > 45 and ≤ 80 mg/d, or if buprenorphine > 8 and ≤ 14 mg/d; and low if methadone > 0 and ≤ 45 mg/d, or if buprenorphine > 0 and ≤ 8 mg/d.
↵† Adjusted for sex (male/female), duration of injection drug use (years), past-month cocaine injection (yes/no), past-month unstable housing (yes/no), past 3- or 6-month incarceration (yes/no), and previous HCV infection (yes/no).