Detection of hepatitis B virus from patients with anti-HBC as the only marker of HBV infection by ultrasensitive PCR

Abstract

The serological diagnosis is the major method to determine hepatitis B virus (HBV) infection. The major serological markers for HBV are HBsAg, Anti-HBs and Anti-HBc. The presence of anti-HBc as the only serological marker for HBV is usually interpreted as follow; low titer of HBV, interference of HBsAg synthesis by coinfection with HCV and mutation of S gene especially in "a" determinant in HBsAg and the past history of infection with undetectable anti-HBs. In order to test this hypothesis we develop ultrasensitive PCR for HBV DNA detection. The clinical specimens are from patients in King Chulalongkorn Memorial Hospital during July 2003 to May 2004. Of the 158 specimens, 8 (5.06%) were HBV DNA positive. Half of the HBV DNA positive samples were detected by ultrasensitive PCR method. All samples have viral load <200 copies/ml when detected by Cobas Amplicor HBV Monitor[superscript TM] Test (Roche Diagnostic,USA). The ultrasensitive PCR can increase the detection sensitivity up to 4 fold. Interference of HCV infection is not involved in our study. The mutation in "a" determinant were found in five samples with amino acid substitution in many positions. According to our finding, the most probable reason of undetectable HBsAg in only anti-HBc positive marker is the very low virus titer which is below the detection limit of the serological assays.