Hepatitis B virus DNA viral load determination in hepatitis B surface antigen-negative Swiss blood donors

BackgroundNucleic acid test (NAT) hepatitisB virus (HBV) screening for all blood donations with a sensitivity limit of 25IU/mL in the individual donation is mandatory in Switzerland since 2009. The aims of the two studies were to define the percentage of antibody to hepatitisB core antigen (anti-HBc) or anti-HBc and antibody to hepatitisB surface antigen (anti-HBs)-positive donors bearing HBV DNA and to gather HBV viral load data on HBV NAT yields during the routine screening since the introduction of the HBV NAT. Study Design and MethodsArchive samples from anti-HBc-positive donors (Group I) were analyzed with a quantitative HBV DNA test and further with anti-HBc and anti-HBs assays. In addition, all the HBV NAT-only-yield samples (Group II) from the routine donor screening performed between July 2007 and May 2013 were included in the study. ResultsFrom the 667 samples investigated (131 donors), three donors (2.3%) had donated eight samples (1.2%) with detectable HBV DNA; however, all had very low viral loads (10IU/mL). From the 1,160,426 donations screened with the routine HBV NAT assay, 16 HBV NAT yields were detected: two window period (WP) and 14 occult hepatitis B infection (OBI) cases. In eight of these positive donations (two WP and six OBI), the HBV viral loads were not more than 10IU/mL, in three cases between 10 and 25IU/mL, and in the remaining five donations between 37and 166IU/mL. ConclusionThe highly sensitive HBV NAT assay with a threshold significantly below 10IU/mL is a valuable alternative to anti-HBc and a less sensitive HBV NAT screening in blood donor screening.