The Korea HIV/acquired immune deficiency syndrome (AIDS) cohort study is a prospective multicenter study with ongoing enrollment of HIV-infected adult patients older than 18 years from 17 hospitals in South Korea (Gachon University Gil Hospital, Seoul St. Mary's Hospital, Hallym University Kangdong Sacred Heart Hospital, Kyungpook National University Hospital, Korea University Guro Hospital, Korea University Ansan Hospital, Seoul Asan Hospital, Soon Chun Hyang University Hospital Seoul, Ajou University Hospital, Severance Hospital, Wonju Severance Christian Hospital, Ewha Womans University Mokdong Hospital, Inha University Hospital, Chungbuk National University Hospital, Hallym University Anyang Sacred Heart Hospital, Hallym University Kangnam Sacred Heart Hospital, and Yeungnam University Hospital). To evaluate the prevalence and epidemiological features of HBV or HCV coinfection among HIV-infected persons, we investigated the presence of HBV surface antigen (HBs Ag) and anti-HCV antibody (Ab). Patients who tested negative for HBs Ag and anti-HCV Ab were defined as HIV mono-infection patients. Among patients with HIV infection, HBV coinfection was defined based on positive test results for HBs Ag and HCV coinfection was defined based on positive test results for anti-HCV Ab. Trained researchers from all centers prospectively collected information every 6 months using a standardized protocol. Information included medical history, socioeconomic status, physical findings, laboratory findings including immunological and virological status, and opportunistic diseases. All participants provided written informed consent and ethics approval was obtained from the Institutional Review Board of each participating institute. This study analyzed data for 1,218 HIV-infected persons enrolled between December 2006 and July 2013.

HIV infection was screened for using enzyme immunoassays (EIA) and confirmed using western blotting. HBV infection was defined based on HBs Ag positivity without protective antibodies. HCV infection was detected via EIA for anti-HCV Ab presence, and reactive samples were confirmed using recombinant immunoblot assay. To evaluate the prevalence and epidemiological features of HBV or HCV coinfections, we used baseline data at the time of registration in the Korea HIV/AIDS cohort study. These data included age, sex, body mass index, race, socioeconomic status, sexual habit, first year of HIV diagnosis, history of smoking and alcohol use, route of transmission, CD4/CD8 count, HIV viral load, ART history, HBV vaccination status, history of liver disease, and serum chemistry at study enrollment.

Continuous variables are presented as medians with interquartile ranges (IQR) and categorical variables are expressed as numbers with percentages. To compare variables between two groups, an independent sample t-test or the Mann-Whitney U test was used for continuous variables, and a Brown-Mood median two-sample test or Fisher's exact test was used for categorical variables. Factors associated with HBV or HCV coinfection were analyzed by univariate and multivariate logistic regression models. Variables with a P value less than 0.25 in baseline characteristic analyses were included in univariate analyses, and multivariate analyses included variables with a P value less than 0.16 in univariate analyses. The relationships between clinical factors and HBV or HCV coinfection were summarized by odds ratios (ORs) and 95% confidence intervals (CIs). Statistical analyses were performed using the SPSS, version 16.0 (SPSS Inc., Chicago, IL, USA). A P value less than 0.05 was considered statistically significant.

Among 1,218 participants, 677 were excluded because of missing data. 541 participants were included for analysis. The prevalence of HBV and HCV coinfection was 5.0% (27/541) and 1.7% (9/541), respectively (Fig. 1). The baseline characteristics of the 541 HIV-infected patients are shown in Table 1. Most patients were men (92.8%) and of Korean ethnicity (98.7%). The median age was 42 years (IQR, 33–51 years). According to a self-reported questionnaire, HIV was transmitted mainly by sexual contact (97.6%), and the proportion of homosexual patients (33.1%) was similar to that of heterosexual patients (36.4%). The median CD4 cell count was 356 cells/mm³ (IQR, 206–512 cells/mm³) and the median HIV viral load was 157 copies/mL (IQR, 20–19,645 copies/mL). 375 patients (69.3%) were treatment naïve.

Among the 541 HIV patients who had results of HBs Ag and anti-HCV Ab testing, 36 patients (6.7%) had HBV or HCV coinfection. There were significant differences in age, sex, transmission route of HIV, history of liver cirrhosis, and HBV vaccination status between HIV mono-infection patients and HBV or HCV coinfection patients. Patients with HBV or HCV coinfection were older than HIV mono-infection patients (median, 45 years; IQR, 37–51 years vs. median, 41 years; IQR, 33–50 years, P <0.039). Patients with liver cirrhosis were more common in the HBV or HCV coinfection group than the HIV mono-infection group (8.3% vs. 0.2%, P = 0.001). In contrast, male sex was more common in the HIV mono-infection patients than the HBV or HCV coinfection patients (93.5% vs. 83.3%, P = 0.037), and the rate of HBV vaccination was significantly different between the HIV mono-infection group and HBV or HCV coinfection group (P = 0.0002).

Univariate logistic regression analysis showed that age, sex, sexual contact, history of liver cirrhosis, and HBV vaccination status were associated with HBV coinfection in HIV patients (Table 2). Sexuality and history of liver cirrhosis were not included in multivariate analysis because of unmatched number of participants. In multivariate analysis, HBV unvaccinated status was an independent risk factor for HBV coinfection (OR = 4.95, 95% CI = 1.43–17.13). Factors associated with HCV coinfection were not analyzed because of small number of HCV coinfection patients.