Abstract

Occult hepatitis B (OBI) was defined as the detection of hepatitis B virus (HBV)
DNA in the liver (with or without HBV DNA in serum) without HBsAg[1].
The prevalence of OBI varies from region to region worldwide. This variability
relies upon the sensitivity of HBV DNA detection assays, the sample size, and the
detection of HBV DNA in liver tissue and serum by nested PCR or real-time PCR.
The prevalence of OBI varies from 1% to 87% in different regions of the world[2],
there is no standard assay for diagnosis of OBI in liver tissue or in serum, and the
only reliable method is the detection of HBV DNA by nested PCR or real-time
PCR[3].
The mutations in the HBsAg gene have been observed among patients coinfected
with hepatitis C virus (HCV)[4].
It has been described that about one-third of patients with chronic HCV infection
had detectable serum HBV DNA but undetectable HBsAg[5]. When the coexistence
of both HBV and HCV genomes occurs in the same hepatocyte, the replication of
HBV is inhibited due to the interference of HCV molecules, which therefore results
in the creation of OBI with low replication of HBV DNA[6].
The presence of OBI in chronic HCV infected patients increases the risk of
HCC[7]. Blood transfusion is a main risk factor for transmission of OBI and the
prevalence of OBI among blood donors varies from country to country provided
that the screening of blood donors is done with less security[8].