الفهرس 
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Abstract
Occult HBV infection(OBI) is defined as the existence of HBV DNA in the serum, cells of the lymphatic system and/or hepatic tissue in the absence of serum HBsAg. Most frequently, occult HBV infection follows resolution of acute hepatitis and continues indefinitely after clearance of HBs Ag and biochemical improvement in liver function. For this reason, this form of infection is termed as residual or secondary occult infection. On the otherhand, primary occult infection defined as exposure to small amounts of hepadnavirus where HBV genome, but not serological markers are detectable in serum and the liver may not be involved.
Occult HBV infection in this study as defined in the literature was considered only in case of presence of HBV DNA with absence of HBs antigenaemia, while resolved infection was considered in case of positivity of Anti-HBc and/or Anti-HBs antibodies with undetectable HBV DNA in sera.
It is reported that there is a high prevalence of occult HBV infection in patients with chronic HCV, hepatocellular carcinoma (HCC), hemodialysis (HD) patients, cryptogenic liver disease, drug injection users, HIV patients and those who underwent frequent blood transfusions e.g. hemophilic patients. Moreover, it has been suggested that occult hepatitis B might affect responsiveness of chronic hepatitis C to interferon therapy and disease outcome.
Occult HBV infection represents a potential transmission source of HBV via blood transfusion or organ transplantation as the routine screening for HBV in blood donations relies solely on serological hepatitis B surface antigen (HBsAg) testing.
We aimed in this study to characterize occult hepatitis B infection among HCC, hemodialysis patients, resistant to-HCV combined interferon-ribavirin therapy and blood donors on serological and molecular basis.
This study was conducted on ninety three (93) subjects attending Mansoura University Hospital. Twenty eight of them were females and 65 were male. All of the patients and blood donors were selected to be HBsAg negative and PCR HCV positive. They were categorized into four groups: patients with HCC, hemodialysis patients and HCV-interferone resistant patients and blood donors.
Venous blood samples were collected from each subject for estimation of liver function, anti HCV antibodies and serological markers of HBV (HBs Ag, antiHBs, HBe Ag, antiHBc IgM and IgG). Also detection of viral genomes including HCV RNA and HBV DNA was carried out. In addition, HBV genotyping in all cases and DNA sequencing in some cases is performed.
The results of the study showed that, the percentage of HBV negative patients among studied groups was (44.4%), (14%), (41.2%) and (70.8%) in the four studied groups respectively.
Occult HBV infection represented (26%), (24%), (29.4%) and (12.5%) respectively. So, occult HBV infection is the highest among HCV-INF resistant group.