常规的筛选供血者的 HBsAg 显著地降低了输血后乙型肝炎的发病率。但是,尽管以最敏感的技术检测供血者的 HBsAg,个别病例仍然发生,其原因是不清楚的。一种可能这些病人不是从输血的来源获得乙型肝炎病毒感染,如暴露于 HBsAg 阳性的病人或医务人员,或医院外接触。另一种可能是某些供血单元有乙型肝炎传染性,虽然检测 HBsAg 阴性。这些单元可 Conventional screening of blood donors for HBsAg significantly reduces the incidence of hepatitis B after transfusion. However, although the most sensitive technique to detect HBsAg in blood donors remains, individual cases still occur, the reason for which is unclear. One possibility is that these patients do not acquire hepatitis B virus infection from sources of blood transfusion, such as exposure to HBsAg-positive patients or medical personnel, or out-of-hospital contacts. Another possibility is that some blood donors have hepatitis B infectivity, although HBsAg is negative. These units can be