Lengths of hepatitis B viremia and antigenemia in blood donors: preliminary evidence of occult (hepatitis B surface antigen-negative) infection in the acute stage.

BACKGROUND: The Japanese Red Cross (JRC) implemented a fully automated pooling and nucleic acid amplification test (NAT) system for testing seronegative donations. The JRC sample repository and repeat blood donations allowed for lookback and follow-up studies of hepatitis B virus (HBV) DNA-positive donors, who tested negative for hepatitis B surface antigen (HBsAg) and anti-hepatitis B core antigen in the JRC screening system.

STUDY DESIGN AND METHODS: From February 1, 2000, to March 31, 2003, 17,314,486 units were tested in 50-sample pools with a semiautomated multiplex assay system (AMPLINAT MPX test, Roche). During this period, 328 HBV DNA-positive donations were found. From 26 of these donors, sequential samples were available at short intervals. This enabled us to examine the dynamics of viral markers in acute HBV infection. The length of detectable periods of plasma viremia and antigenemia were estimated by regression analysis from the results obtained in the quantitative polymerase chain reaction assay (JRC) and HBsAg enzyme immunoassay (Auszyme II, AxSYM, Abbott) and chemiluminescence immunoassay (Abbott).

RESULTS: The median length of detectable HBV DNA in individual donation and 20-sample minipool (MP) NAT format was estimated to be 74 and 50 days, respectively, whereas the median length of detectable HBsAg was estimated to be 42 days. Six of the 26 donors were infected with mutant viruses, and 3 of these 6 donors did not develop detectable HBsAg during the entire observation period, despite a moderately high viral load of 10(4) to 10(5) HBV DNA copies per mL.

CONCLUSION: Transmission of mutant virus may cause occult HBV infection in the acute stage. HBV NAT, even in MP configuration, is more effective than HBsAg testing and capable of interdicting infected donors in the pre- and post-HBsAg window periods.