Background:  Occult hepatitis B virus (HBV) infection is diagnosed when HBc antibodies (HBcAb) and HBV DNA is detectable in serum, while hepatitis B surface antigen (HBsAg) is not. This situation has been frequently described in patients with chronic hepatitis C virus (HCV) infection. The objective of this study was to evaluate the prevalence of occult hepatitis B in HIV/HCV-co-infected patients and its clinical relevance in the liver histology and viral response after interferon therapy for the HCV.

Methods:  We included 238 HIV/HCV-co-infected patients who were evaluated before starting HCV therapy. All of them were negative for the HBsAg. Serum samples were analyzed for the presence of HBcAb and HBV DNA. Quantification of HBV DNA was determined with the Cobas TaqMan HBV Test with detection limit of 6 IU/mL. Data resulted from liver biopsy and laboratory liver tests were also analyzed.

Results:  Of our patients, 142 (60%) were HBcAb positive. The independent factors associated with the presence of HBcAb were:  male gender, previous history of intravenous drug use, age, CD4 count, and presence hepatitis A virus (HAV) antibody. Among 90 HBcAb⁺ patients that we could analyze, HBV DNA were positive in 15 (16.7% of occult hepatitis B infection). No baseline factors (including transaminase levels or plasma HCV RNA load), liver histology, or HCV therapy response were related with the presence of HBV DNA.

Conclusions:  We found that occult hepatitis B is a  frequent condition present in >16% of our HCV/HIV-co-infected patients, but this phenomenon seems not to  affect the clinical evolution of chronic hepatitis C or  modify the viral response to Interferon-based HCV therapies.