Why is incubation omitted in the direct antiglobulin test?

In the direct antiglobulin test (DAT), incubation is omitted because the antigen-antibody complex has already formed in vivo within the patient's body. This test is used to detect antibodies that are bound to the surface of red blood cells, typically as a result of autoimmune hemolytic anemia or transfusion reactions. Since the antibodies are already attached to the antigens on the surface of the red blood cells when the sample is obtained, further incubation is unnecessary and does not provide any additional benefit to the test.

By omitting incubation, the test simplifies the procedure and allows for a more rapid assessment of the presence of bound antibodies without the risk of inducing further reactions or artifacts that could arise during incubation. Therefore, the focus is directly on detecting those antibodies that are already present in the sample without the potential complications that incubation could introduce.