in cross-matching, atypical antibodies in the blood plasma of pregnant women as part of antenatal care, and detection of antibodies for the diagnosis of immune-mediated haemolytic anemias. Coombs tests are performed using RBCs or serum (direct or indirect, respectively) from venous whole blood samples which are taken from patients by venipuncture. The venous blood is taken to a laboratory (or blood bank), where trained scientific technical staff do the Coombs tests. The clinical significance of the result is assessed by the physician who requested the Coombs test, perhaps with assistance from a laboratory-based hematologist. Direct Coombs test The direct Coombs test, also referred to as the direct antiglobulin test (DAT), is used to detect if antibodies or complement system factors have bound to RBCs surface antigens. The DAT is not currently required for pre-transfusion testing but may be included by some laboratories. Pre-transfusion, patients often have an indirect Coombs test. Uses The direct Coombs test is used clinically when immune-mediated hemolytic anemia (antibody-mediated destruction of RBCs) is suspected. A positive Coombs test indicates that an immune mechanism is attacking the patient's RBCs. This mechanism could be autoimmunity, alloimmunity or a drug-induced immune-mediated mechanism. Examples of alloimmune hemolysis Hemolytic disease of the newborn (also known as HDN or erythroblastosis fetalis) Rh D hemolytic disease of the newborn (also known as Rh disease) ABO hemolytic disease of the newborn (the direct Coombs test may only be weakly positive) Anti-Kell hemolytic disease of the newborn Rh c hemolytic disease of the newborn Rh E hemolytic disease of the newborn Other blood group incompatibility (RhC, Rhe, Kidd, Duffy, Lewis, MN, P and others) Alloimmune hemolytic transfusion reactions Examples of autoimmune hemolysis/immunohemolytic hemolysis Warm antibody autoimmune hemolytic anemia Idiopathic Systemic lupus erythematosus Evans' syndrome (antiplatelet antibodies and hemolytic antibodies) Cold antibody immunohemolytic anemia Idiopathic cold hemagglutinin syndrome Waldenström's macroglobulinemia Infectious mononucleosis Paroxysmal cold hemoglobinuria (rare) Drug-induced immune-mediated hemolysis Methyldopa (IgG mediated type II hypersensitivity) Penicillin (high dose) Quinidine (IgM mediated activation of classical complement pathway and Membrane attack complex, MAC) (A memory device to remember that the DAT tests the RBCs and is used to test infants for haemolytic disease of the newborn is: Rh Disease; R = RBCs, D = DAT.) Laboratory The patient's RBCs are washed (removing the patient's own serum) and then centrifuged with antihuman globulin (also known as Coombs reagent). If immunoglobulin or complement factors have been fixed on to the