Blood donation and will screen for antibodies to less common antigens. More testing, including a crossmatch, is usually done before a transfusion. Type O negative is often cited as the "universal donor" but this only refers to red cell and whole blood transfusions. For plasma and platelet transfusions the system is reversed: AB positive is the universal platelet donor type while both AB positive and AB negative are universal plasma donor types. Most blood is tested for diseases, including some STDs. The tests used are high-sensitivity screening tests and no actual diagnosis is made. Some of the test results are later found
Blood doping cells into surrounding tissue during each passage through the cardiovascular system. ITPP has been a subject of anti-doping research in both humans and racehorses. Blood transfusions can be traditionally classified as autologous, where the blood donor and transfusion recipient are the same, or as allogeneic/homologous, where the blood is transfused into someone other than the donor. Blood transfusion begins by the withdrawal of 1 to 4 units of blood (1 unit = 450 ml of blood) several weeks before competition. The blood is centrifuged, the plasma components are immediately reinfused, and the corpuscular elements, principally red blood cells (RBCs), are