Background: Occult hepatitis B is defined by the presence of the hepatitis B virus (HBV)-DNA in a
serum or in the liver tissue in the absence of hepatitis B surface antigen (HBsAg). The prevalence and clinical
correlates of occult hepatitis B remain incompletely defined. This cross-sectional study was carried out to determine
the prevalence of occult hepatitis B with chronic hepatitis C disease in Thailand.
Method: Using the polymerase chain reaction, we searched for HBV DNA in formalin-fixed liver samples
from 49 HBsAg-negative patients with hepatitis C virus (HCV)-related chronic hepatitis. Twenty-three patients
had detectable antibodies to the HBV core antigen (anti-HBc) while another fourteen patients had no detectable
antibodies. We also studied five HBsAg-positive patients as a control group.
Results: Intrahepatic HBV DNA was not detected in 50 specimens examined by nested PCR to identify
HBV DNA and HBV genotype. In HBsAg-positive control groups, HBV DNA was detected in three of five
Conclusions: A very low occult HBV infection rate was found in HCV Thai patients, but this may be not
a true prevalence of occult HBV. Fresh frozen liver tissue or peripheral mononuclear cell may be a better sample
for HBV testing. For future study, a new nested PCR technique to detect HBV DNA for other organs should be
developed to evaluate the “true prevalence” of occult HBV infection.