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Definition

Blood typing is a laboratory test that identifies blood group antigens (substances that stimulate an immune response) belonging to the ABO blood group system. The test classifies blood into four groups designated A, B, AB, and O. Antibody screening is a test to detect atypical antibodies in the serum that may have been formed as a result of transfusion or pregnancy. An antibody is a protein produced by lymphocytes (nongranular white blood cells) that binds to an antigen, facilitating its removal by phagocytosis (or engulfing by macrophages) or lysis (cell rupture or decomposition). The type and screen (T&S) is performed on persons who may need a transfusion of blood products. These tests are followed by the compatibility test (cross-match). This test insures that no antibodies are detected...