FDA test requirements (with American Red Cross guidance):
Hepatitis B virus (HBV):  The tests used for blood donor screening are the GS HBsAg EIA 3.0, a qualitative ELISA for the detection of Hepatitis B Surface Antigen (HBsAg), and the Ortho HBc ELISA for the qualitative detection of antibody to HBV core antigen (anti-HBc) in human serum and plasma samples.  An FDA licensed triplex nucleic acid test (NAT) using transcription-mediated amplification was introduced by the Red Cross in 2009. The assay detects HBV DNA, HIV-1 RNA, and HCV RNA.  The frequency of detecting an active HBV infection in a blood donor is about 1 per 12,000 donations screened. The per-unit risk of HBV infection through blood transfusion is less than 1 per million units screened.  Hepatitis C (HCV): The test used for blood donor screening is the Ortho HCV ELISA for the qualitative detection of antibody to HCV antibodies (anti-HCV) in human serum or plasma samples. A duplex nucleic acid test (NAT) was introduced for HIV-1/HCV RNA detection in 1999 and updated to include the detection of HBV DNA in 2009. Donors who test HCV-antibody reactive, but NAT nonreactive by routine testing are further tested individually for HCV RNA by NAT. Donors who test anti-HCV and HCV NAT reactive do not require further testing.  The frequency of detecting a positive donor is about 1 per 5,000 donations screened. The per-unit risk of HCV infection through blood transfusion is less than 1 per 2 million units screened.  HIV: The test used for blood donor screening is the GS HIV-1/HIV-2 PLUS O EIA for the simultaneous qualitative detection of anti-HIV 1 (groups M and O) and/or HIV-2 in human serum or plasma.   A duplex nucleic acid test (NAT) was introduced for HIV-1/HCV RNA detection in 1999 and updated to include the detection of HBV DNA in 2009. Donors who test antibody reactive are further evaluated by additional tests to confirm the presence of HIV antibody and to differentiate HIV-1 from HIV-2 antibodies.  Donors who test anti-HIV-1/HIV-2 and HIV-1 NAT reactive are not further tested. The frequency of detecting HIV-1 in a blood donor is about 1 per 33,000 donations screened.  detecting HIV-2 in a blood donor is extremely rare at 1 per 57 million donations, with only 5 such infected donors ever identified since HIV-2 screening began in 1992. The per-unit risk of HIV-1 infection through blood transfusion is less than 1 per 2 million units screened.  Human T-cell lymphotropic virus I/II (HTLV-I/II): The test used for blood donor screening is the Avioq HTLV-1/2 Microelisa system for the qualitative detection of antibodies to HTLV-1 and HTLV-2 in human serum or plasma samples. Donors who test reactive for anti-HTLV-1/2 are further tested using an FDA licensed western blot to determine if antibodies are present.  There are no nucleic acid tests (NAT) available for HTLV-1/2. The per-unit risk of transfusion-transmitted HTLV-1/2 is less than 1 per 2 million units screened, and the frequency of detecting an infected donor is 1 per 27,000 donations screened. Syphilis: Screening for syphilis is performed using a qualitative test that detects the presence of antibodies to the spirochete (corkscrew-shaped bacterium), Treponema pallidum, by an automated agglutination assay based on specific pattern recognition. C Confirmation is performed using another serologic test for total antibodies, an enzyme-linked immunoassay, as well as a test for reagin (a protein-like substance that is present during acute infection and for several months following resolution of infection).  No cases of transfusion-transmitted syphilis have been recorded in more than 50 years.  West Nile virus (WNV): WNV RNA is detected by an FDA licensed NAT assay similar to that used for HIV-1, HCV, HBV, and Zika virus.  NAT-reactive donations are further tested by repeat NAT and antibody to confirm infection.  Following the introduction of blood donor screening, there have been 15 cases of transfusion transmission from screened blood; all are believed to be due to donations having very low levels of virus. This translates to a risk of about 1 per 84 million donations for the Red Cross overall (or 1 per 35 million during the summer transmission season).  Trypanosoma cruzi: The Red Cross blood donations are screened using the Ortho T. cruzi Enzyme-Linked Immunosorbent Assay (ELISA) for the qualitative detection of antibodies to T. cruzi in human serum or plasma samples. An FDA licensed enzyme strip immunoassay (ESA) is used for confirmatory testing. Because T. cruzi is not endemic in the United States, the Red Cross (and all US blood centers) donors are tested only once. The frequency of detecting a positive donor is about 1 per 15,000 first-time donations screened. Babesiosis:  In May 2018, the Red Cross began testing from whole blood samples using a NAT assay that detects the main four species of babesia pathogenic to humans. The assay, now FDA licensed, detects ribosomal RNA of the parasite following red cell lysis, significantly increasing sensitivity and obviating the need for antibody testing. Tested in 14 states in the US where incidence of infection is highest.