Which test is typically used to confirm the presence of alloantibodies in a serum sample?

The test commonly employed to determine the presence of alloantibodies in a serum sample is the antibody screen. This test works by exposing the patient's serum to a panel of red blood cells with known antigens. If the serum contains alloantibodies—antibodies that react against the antigens present on transfused blood cells—these antibodies will bind to the corresponding antigens on the test cells, leading to agglutination or hemolysis. This response confirms the presence of specific antibodies.

The antibody screen is crucial in transfusion medicine because it helps identify potential incompatibilities when matching blood types for transfusion, ensuring patient safety by preventing transfusion reactions.

While other tests like crossmatching and the direct antiglobulin test are valuable in different contexts, they are not primarily designed for detecting alloantibodies. Crossmatching is performed after identifying antibodies to ensure compatibility between the donor and recipient blood. The direct antiglobulin test assesses whether antibodies are bound to the patient’s red blood cells, whereas the indirect antiglobulin test is used mainly to detect free antibodies in the serum but is not the primary method for screening for alloantibodies.