doi:10.1038/nindia.2010.118 Published online 30 August 2010
If blood donors are screened only for the hepatitis B surface antigen HBsAg, there is a chance that the hepatitis B virus (HBV) might stealthily pass on viremic units into the public blood supply, according to a new study. The study suggests introduction of a second line of screening to make blood donation completely HBV infection-free.
The result also points to the alarming reality that a considerable number of HBV infected donors remain undiagnosed of the condition that leads to the life-threatening liver infection.
Researchers from three Kolkata-based bodies — the virus unit of Indian Council of Medical Research, National Institute of Cholera and Enteric Diseases and Jadavpur University — tested 729 HBsAg negative or antiHBc positive donors and tried to detect any presence of occult HBV infection in them. Occult HBV infection is the detection of potentially infectious HBV DNA in the liver, serum, or both, in individuals without detectable HBsAg. AntiHBc is the only seromarker for HBV infection.
India is estimated to have over 40 million chronic carriers of the virus. Despite testing for HBsAg in blood donors, transfusion-associated HBV continues to be a major problem in India. HBV infection is detected among blood donors by screening for HBsAg with commercial enzyme immuno assay. However, this has failed at times due to the presence of occult HBV infection.
The researachers chose Ganjam in the state of Orissa for the study following a National AIDS Control Organization (NACO) report listing the district among one of the highest HIV prevalent districts of India. They collected samples from the only blood bank in the district. The idea was to evaluate the prevalence of occult HBV infection among the HBsAg negative donations from the highly HIV prevalent region.
They used an in-house nucleic acid test (NAT) for detection of occult HBV infection and sequenced and analysed the surface gene of the virus. Around 30% HBsAg negative donors turned out to be antiHBc positive.
"Although addition of antiHBc testing, will lead to rejection of a large number of donor units; it will definitely eliminate HBV infected donations," the authors say in their paper.