Antibody screening is the most convenient and sensitive method used for the detection of clinically important antibodies. This test includes antibodies to Human IgG and C3. The antihuman globulin test is used in different ways in pre-transfusion and compatibility testing. Direct Antiglobulin Test (DAT) is used to detect antibodies on patient erythrocytes and in-vivo sensitization. Erythrocyte alloantibodies destroy erythrocytes by activating complement causing lysis.