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any of a number of tests to ascertain the presence or absence of immunoglobulin and complement in the coating of erythrocytes. Rabbit antihuman serum is used to act as a bridge between sensitized cells, yielding agglutination (a positive result). The tests can be used to differentiate between various types of hemolytic anemias, to determine minor blood types including the Rh factor, and to test for anticipated erythroblastosis fetalis.
direct Coombs' test the test used to detect in vivo sensitization of red blood cells and formation of cell-bound antibodies that may damage erythrocytes but will not cause visible agglutination. The erythrocytes are washed free of serum and unbound antibody, and antiglobulin (antiserum directed against human antibodies and complement components) is added. Agglutination indicates the presence of antibody. Clinically its most important use is in early diagnosis of erythroblastosis fetalis and autoimmune hemolytic anemias. It is used also in crossmatching blood for transfusions. Venous blood or blood from the umbilical cord may be used.
indirect Coombs' test a test for detecting antigen-antibody reactions that occur in vitro; used to determine incompatibility in transfusions when the recipient has a greater than normal risk of transfusion reaction. It uses antiglobulin serum to detect the in vitro sensitization of red blood cells by serum. The test also can reveal the presence of anti-Rh antibodies in maternal blood during pregnancy. Either clotted blood or blood with an anticoagulant may be used. The patient's serum is incubated with donor red blood cells, the cells are washed, and antiglobulin added. Agglutination indicates the presence of incomplete sensitizing antibodies in the serum.