RESUMO
BACKGROUND: The aim of this study was to detect DNA of hepatitis B virus (HBV) for reliable diagnosis of HBV infection in sera by means of a validated polymerase chain reaction (PCR) using a 5' oligonucleotide (primer) previously described and a 3' primer designed by our investigation group. METHODS: Sera samples collected from patients with chronic liver disease (CLD) related to HBV infection and negative to hepatitis C virus (HCV) infection were analyzed. Patients were both positive and negative to HBV by serum markers detected by ELISA immunoassay. A 146-base pair (bp) fragment was amplified from highly conserved precore-core region. This procedure enabled us to search for DNA HBV-positive cases. RESULTS: Viral replicative state in negative hepatitis B e antigen (HBeAg) (15.7%) cases was verified by PCR technique. This detected infection by HBV in 100% of immunoassay-positive samples. Additionally, sequences of expected size in patients bearing atypical markers in their sera (7.1%) and those with negative serology (4.8%) for HBV markers were detected. CONCLUSIONS: In this study we have improved a PCR technique successfully applied in hepatitis B prevalence studies in northeastern Mexico. Prevalence of hepatitis B in this region of Mexico is intermediate compared to countries of the northern hemisphere where prevalence is lower, and to countries of Southeast Asia and the Mediterranean region where it is highly endemic.