Flow cytometry
In 2004, a test for detection allogeneic/homologous blood transfusion doping was implemented. Flow cytometry is the method of choice. By examining markers on the surface of blood cells, the method can determine whether blood from more than one person is present in an athlete's circulation. The test utilizes 12 antisera directed against the blood group antigens, obtained from donor plasma. The antigens are labeled with secondary antibodies, which are conjugated with phycoerythrin to label IgG or IgM-coated RBCs and enhance the detection by flow cytometry The flow cytometry is able to detect minor variance in blood group antigens. The assessment was able to distinguish the blood of subjects who had earlier received at least one unit of allogeneic blood. This technique is able to detect small (&lt;5%) populations of cells that are antigenically distinct from an individual's own RBCs.