HIV-positive people may test negative for both hepatitis B virus (HBV) surface antigens and surface antibodies, but be positive for HBV core antigens, particularly if they are coinfected with hepatitis C virus (HCV), according to a US study published in the June 15th edition of Clinical Infectious Diseases.
The study involved 651 HIV-positive patients receiving care at three hospitals in Boston. A total of 387 patients (59%) tested negative for both HBV surface antigens and antibodies, of these 142 underwent further testing for HBV core antigen. Of these 60 (42%) tested positive.
Coinfection with HIV and HCV was present in 78.3% of these patients, and 77.6% had a history of injecting drug use.
In univariate analysis alanine aminotransferase (ALT) levels were higher in patients testing positive for HBC core antigen (median 47 versus 24 in patients testing negative, p=.001).
In multivariate analysis elevated ALT levels ceased to be associated with being HBV core antigen-positivity. Nor was association found with CD4 cell count, or HIV viral load. The only significant relationship to be established was with HCV coinfection (adjusted OR, 25.9; p<.0001>
The investigators note that HBV testing in HIV-positive patients using tests for surface antigen and antibodies “will miss a large number of individuals with isolated anti-HBc.” They add that the factors associated with detecting HBV core antibodies in HIV-positive patients were HCV coinfection and injecting drug use, two “clearly related factors.”
Possible explanations for the high prevalence of HBV core antigen in HIV-positive patients are provided by the investigators. First, patients may have cleared HBV infection and lost surface antibodies. In addition, HIV-positive patients can lose antibodies to HBV as a result of suppressed immune function. The investigators discount this as a factor affecting the findings of their study, as neither CD4 cell count nor viral load was found to be associated with testing positive for core antigen.
An alternative reason could be “occult infection with HBV in a group of individuals with a high prevalence of risk factors for HBV infection, such as injection drug use or risky sexual behavior.”
A third explanation is provided by the investigators for patients who test positive for HBV core antigen but negative for HBV DNA. This could be due either to clearance of HBV infection or a false-positive result caused by cross-reacting antibodies in HCV-coinfected patients.
The investigators note in their conclusion that the clinical significance of their findings are not certain. However they stress that “more than 75% of individuals coinfected with HIV-1 and HCV who do not have serological evidence for HBV when screened for surface antibodies and antigen will test positive for HBV core antigen.”
Further information on this website
Hepatitis B - overview
Hepatitis C – overview
Hepatitis B - factsheet
Hepatitis C - factsheet
HIV and hepatitis - booklet in the information for HIV-positive people series
Gandhi RT et al. Isolated antibody to hepatitis B core antigen in human immunodeficiency virus type-1-infected individuals. Clinical Infectious Diseases 36: 1602 – 1605, 2003.