Table 2.
Logistic regression models* to identify determinants of prevalence of antibodies to hepatitis B core antigen, hepatitis C virus, and HIV
| Total sample (n=1193)† | No (%) positive for antibodies | Odds ratio (95% CI) | P value‡ | |
|---|---|---|---|---|
| Antibodies to hepatitis B core antigen (n=104) | ||||
| Ever injected drugs: | ||||
| No | 669 | 10 (1.5) | 1 | |
| Yes | 509 | 94 (18.5) | 21.6 (10.9 to 47.6) | <0.0001 |
| Age (years): | ||||
| 16-19 | 177 | 9 (5.1) | 1 | |
| 20-24 | 367 | 26 (7.1) | 1.5 (0.6 to 4.1) | 0.41 |
| 25-34 | 399 | 37 (9.3) | 2.3 (1 to 6.3) | 0.07 |
| ⩾35 | 194 | 27 (13.9) | 9.7 (3.8 to 28.6) | <0.0001 |
| Ever treated for sexually transmitted infection: | ||||
| No | 1011 | 75 (7.4) | 1 | |
| Yes | 147 | 26 (17.7) | 1.9 (1.1 to 3.3) | 0.02 |
| Antibodies to hepatitis C virus (n=442) | ||||
| Ever injected drugs: | ||||
| No | 669 | 25 (3.7) | 1 | |
| Yes | 509 | 414 (81.3) | 80.8 (47.9 to 143) | <0.0001 |
| Age (years): | ||||
| 16-19 | 177 | 47 (26.6) | 1 | |
| 20-24 | 367 | 175 (47.7) | 2.8 (1.5 to 5.3) | 0.002 |
| 25-34 | 399 | 158 (39.6) | 1.8 (0.9 to 3.4) | 0.08 |
| ⩾35 | 194 | 38 (19.6) | 1.9 (0.8 to 4.5) | 0.11 |
| Months spent in prison over past 10 years: | ||||
| <3 | 136 | 20 (14.7) | 1 | |
| 3-11 | 197 | 39 (19.8) | 2.9 (1.2 to 6.9) | 0.01 |
| 12-36 | 299 | 102 (34.1) | 4.0 (1.9 to 8.6) | <0.001 |
| >36 | 538 | 277 (51.5) | 6.5 (3.2 to 13.3) | <0.0001 |
| Smoked heroin in past 12 months: | ||||
| No | 637 | 82 (12.9) | 1 | |
| Yes | 540 | 353 (65.4) | 2 (1.2 to 3.3) | 0.007 |
| Antibodies to HIV (n=24) | ||||
| Ever injected drugs: | ||||
| No | 669 | 6 (0.9) | 1 | |
| Yes | 509 | 18 (3.5) | 3.4 (1.3 to 9.5) | 0.01 |
| Ever treated for sexually transmitted infection: | ||||
| No | 1011 | 15 (1.5) | 1 | |
| Yes | 147 | 9 (6.1) | 3 (1.2 to 7.4) | 0.02 |
| Men ever had anal sex with men: | ||||
| No | 1080 | 18 (1.7) | 1 | |
| Yes | 28 | 5 (17.9) | 8.4 (2.4 to 25.1) | 0.001 |
Initial models for hepatitis C and HIV included age, sex, time spent in prison in the past 10 years, injecting drug use, smoking heroin, ever had sex with a man inside or outside prison, ever treated for sexually transmitted infection, and use of condoms during heterosexual intercourse. Model for hepatitis B also included whether respondents had started or completed hepatitis B vaccination. Significant factors were retained in the final model.
Numbers do not always add up to total because not all respondents answered all questions.
For whole model χ2=142, P<0.0001 for hepatitis B core antigen; χ2=848, P<0.0001 for hepatitis C virus, and χ2=28, P<0.0001 for HIV.