![]() This leaves an approximate period of 2 to 3 weeks when an infected donor may not be detected by blood donation screening. NAT has reduced the window-period from HBV infection to detection by about 12 days. ![]() The per-unit risk of HBV infection through blood transfusion (chance of releasing an infectious blood component) is approximately 1 per million units screened using published data through 2019, and this number has remained stable. False-positive donors for any HBV marker may be reentered. If neutralization testing is positive and MP-NAT is nonreactive, or the donation sample is anti-HBc-reactive and HBsAg and MP-NAT are nonreactive, further testing is performed by HBV individual donation NAT. Specific antigen neutralization is used for confirmation of HBsAg reactivity HBsAg-reactive samples that are HBV DNA reactive do not require further testing by neutralization. Testing is performed in mini-pools (MPs) of 16 samples components of reactive MPs are tested individually to identify the reactive donations, followed by virus-specific testing to determine the virus responsible for the sample's reactivity. The assay detects HBV DNA, HIV RNA, and HCV RNA. An FDA licensed triplex NAT using transcription-mediated amplification was introduced by the Red Cross in June 2009. The tests used for blood donor screening are the GS (Genetic Systems’ distributed by Ortho) HBsAg EIA 3.0, a qualitative ELISA for the detection of HBsAg, and the Ortho HBc ELISA for the qualitative detection of antibodies to HBV core antigen (anti-HBc) in human serum and plasma samples. Anti-HBc appears in the blood of individuals infected with HBV one to four weeks after the appearance of HBsAg, and at the onset of symptoms for those adults who develop symptoms (5% or less). HBV DNA and HBsAg are the first viral markers to circulate in an individual infected with HBV. The frequency of detecting a positive donor is about 1 per 15,000 first-time donations screened. cruzi is not endemic in the US without any incident cases in blood donors, the Red Cross (and all US blood centers) are allowed to test donors only once. None of these transfusion transmissions (n=11 combined for the US and Spain from 1987-2011) were associated with an incident or autochthonous donor infection. All reports of transfusion transmission in the United States and Spain (another country with a high number of residents having lived in endemic areas of the Americas) have been from unscreened whole blood, platelets (including leukoreduced and irradiated), except from one red cell case, or from whole blood from unscreened donors in Latin America. cruzi can be transmitted by blood transfusion, to date, the Red Cross has not identified any recipients infected by blood components from screen-negative donors or screen-negative donors who subsequently tested positive (seroconverted). cruzi reentry algorithm requiring a follow-up sample testing nonreactive by the two FDA-licensed screening tests and the ESA. An FDA-licensed enzyme strip immunoassay (ESA) is used for confirmatory testing. cruzi Enzyme-Linked Immunosorbent Assay (ELISA) for the qualitative detection of antibodies to T. The Red Cross blood donations are screened using the Ortho T. The agent is endemic in Latin America, but approximately 20 reports of transmission by blood transfusion have been published worldwide. The parasite Trypanosoma cruzi Is the causative agent of Chagas disease, a serious illness.
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