Where prehospital transport times are high, patients are often admitted for surgery exsanguinated after post-partum and post-injury hemorrhage, and need urgent blood transfusion at the district hospital. However, most low-income countries report high prevalence rates of hepatitis B virus (HBV) infection: 20% in Bangladesh, 12% in Cambodia, 12% in Vietnam. These prevalence estimates are based on identification of live virus by plasma screening tests for HBV surface antigen (HBsAg).
The challenge: “Hidden” HBV infection
The trouble is that HBV infection can be transmitted by blood transfusion also from donors where live HB virus can not be detected, HBsAg-negative donors. The reason seems to be that HBV is present and replicating in the liver, producing detectable DNA, but not detectable HBV surface antigen in plasma. HBV core antibodies (HBcAB), however, is present in plasma. In a pilot screening of potential blood donors in Cambodia TCF found 48% prevalence of HBsAg-negative HBcAb-positive potential donors. There are thus good reasons to believe that published prevalence rates from South-East Asia seriously underestimate the extent of the HBV problem in the area. And underestimate the risk of blood transmitted HBV infection accordingly.
Exclusion of blood donors with hidden HBV infection (healthy patients with negative HBsAg screening tests but positive HBcAb) is routine in Western countries – and HBcAb positive donors excluded. But so far such requirements are not set by WHO for SE Asia.
TMC with partners are now conducting a major multi-center study in Vietnam and Cambodia to develop evidence-based guidelines for safe blood services in areas where hepatitis B and C virus infections are endemic. The study aims are to get solid prevalence estimates of HCV and “hidden” HBV infection, and to test accuracy of cheap rapid tests for screening of blood donors.