Objectives: Hepatitis B surface antigen (HBsAg) is often used as the serological marker to screen for hepatitis B virus (HBV) infection in the investigation of liver cirrhosis. In Hong Kong, where HBV infection is endemic, some patients may have persistent viral infection after the loss of HBsAg. We aimed to investigate 1) the prevalence of occult HBV infection in cryptogenic liver cirrhosis in Hong Kong and 2) the role of HBV "a" determinant mutations among these patients.
Methods: Twenty-eight patients with cryptogenic liver cirrhosis (group I), 49 subjects with no liver disease (group II), and 26 patients with HBV-related cirrhosis (group III) were studied. HBV DNA was determined by the cross-linking assay (sensitivity = 0.5 mEq/ml) and polymerase chain reaction (PCR). Occult HBV infection was defined as HBV DNA detectable by PCR among patients with negative HBsAg.
Results: Eighty-nine percent and 92% of patients in groups I and II, respectively, had positive anti-HBs and/or anti-hepatitis B core. Nine (32%), no (0%), and 14 (54%) patients in groups I, II, and III, respectively, had detectable HBV DNA by PCR (group I vs group II, p < 0.001; group I vs group III, p = 0.36). Four patients in group I had HBV DNA detectable by the cross-linking assay (median = 5.98 mEq/ml, range = 3.1-8.01). "a" determinant mutations were detected in two patients in group I (K122N and G145R, C125A) and one patient in group II (1126N).
Conclusions: Occult HBV infection is common among patients with cryptogenic liver cirrhosis, and it cannot be explained by mutations in the HBV "a" determinant.