The epidemiology and natural history of Hepatitis C infection in a cohort of homosexual men (1982-1998)

Objectives: The objectives of this study were: (1) to estimate the prevalence and incidence of hepatitis C virus (HCV) infection among all gay men residing in Vancouver during the period 1982-98, (2) to identify risk factors for HCV infection and predictors of 'time to HCV seropositivity' in this population, and (3) to determine whether coinfection with HCV adversely influences the natural history of HIV infection in coinfected men. Methods: The Vancouver Lymphadenopathy-AIDS Study (VLAS) has monitored a cohort of homosexual men since November 1982. Serum samples were obtained from 932 men during the period 1982-98, and tested for HCV antibody using EIA1, EIA2, and RIBA. HIV-antibody test results were also available. Data regarding demographic variables, sexual practices, substance use, and history of infectious diseases were obtained from self-administered questionnaires completed during 1982-85. Data regarding HIV-related disease progression were also available including clinical symptoms and signs, physical findings, CD4 cell count, diagnosis of AIDS, and survival. Risk factors for HCV infection were assessed for statistical significance using both cross-sectional comparisons of seropositive and seronegative men and prospective analyses of time to HCV seropositivity. Differences in time to HCV seropositivity, AIDS progression and survival were evaluated by stratified Kaplan-Meier analysis, and tested using the log-rank test. Both logistic regression and Cox proportional hazards regression were used to model the simultaneous effect of several variables on outcomes of interest. All p-values were two-sided. Results: A total of 54 of 932 men (5.8%) tested positive for HCV antibody [95% CI: 4.3%, 7.3%]. HCV prevalence was significantly higher among HIV seropositive men compared to HIV seronegative men (8.8% vs. 2.6%; p<0.001). After 14 years of follow up, cumulative HCV incidence in the cohort was 7.9% [95% CI: 5.1%, 10.7%]. Annual infection rates ranged from 0 to 1.4 percent during the follow-up period. Men who reported using injection drugs during their lifetime were twenty times more likely to be become HCV seropositive. In prospective analyses, significant elevations in risk were detected for the following sexual practices: 20 or more male sexual partners in the previous 12 months [RR = 3.1, 95% CI: 1.5, 6.3], insertive oral-anal contact [RR = 3.1, 95% CI: 1.1, 8.7], insertive fisting (RR = 2.6, 95% CI: 1.4, 4.8), and receptive anal intercourse [RR = 2.0, 95% CI: 1.0, 3.8]. In multivariate analysis, risk factors that exerted an independent effect on time to HCV seropositivity were injection drug use (p