A major goal of transfusion medicine practice has been to reduce the risk of transfusion-transmitted infection to as low a level as possible . This discussion will provide a general overview of the blood donor medical history as a means for screening donors in the United States for the possibility that their blood products might transmit such infections. Issues related to the actual procedures involved in blood donor screening and the laboratory testing of donated blood are discussed separately. (See "Procedures used for blood donor screening: Protection of potential blood donors and recipients" and "Laboratory testing of donated blood".)
Donor screening and laboratory testing of donated blood prior to transfusion are intended to ensure that recipients receive the safest possible blood products. As of 2009, such testing consists of determining the ABO blood group and Rh blood type of the donated unit, testing for red cell antibodies, and performing infectious disease screening for the following agents: HIV-1, HIV-2, human T-lymphotropic virus (HTLV)-I, HTLV-II, hepatitis C virus, hepatitis B virus, West Nile Virus (WNV), and T. pallidum (syphilis) (table 1).
In addition, many blood collection agencies screen for antibody to Trypanosoma cruzi, the causative agent of Chagas disease. All infectious disease screening assays must be negative in order to release the blood unit or its components to hospitals for transfusion.
Since 1999, standard serological testing of donated blood for the human immunodeficiency virus (HIV) and hepatitis C virus (HCV) has been supplemented by the addition of nucleic acid testing of pools of donations for HIV and HCV RNA, which allows for detection of additional infectious units .
Risk of viral infection from transfusion — The current per unit risk estimate for acquiring HIV from transfusion is one in 1.5 to 2.1 million, and for HCV is one in 1.1 to 1.9 million [3,4]. Risks for hepatitis B virus (HBV) are more difficult to determine, since there are more unknowns in the mathematical model; current estimates range from one in 205,000 to one in 355,000, and are lower than the mid-1990s estimate of one in 63,000 [3,5,6]. The risk for HTLV is estimated to be about one in two million when the older published risk estimate (one in 641,000) is adjusted for the fact that only one-third of potentially infectious units actually transmit HTLV infection, due to loss of viable virus upon blood component storage (table 1) and (see "Transfusion transmitted HIV infection and AIDS" and "Laboratory testing of donated blood") [5,7].