What is the purpose of using the antiglobulin reagent in the direct antiglobulin test?

The purpose of using the antiglobulin reagent in the direct antiglobulin test is to detect preexisting antibodies on erythrocytes. This test is specifically designed to identify whether antibodies or complement proteins are bound to the surface of red blood cells.

When a sample of red blood cells is mixed with the antiglobulin reagent, typically anti-human globulin (also known as Coombs' reagent), it will interact with any antibodies that are already attached to the red cells. If such antibodies are present, the antiglobulin reagent will cause agglutination (clumping) of the red cells, indicating a positive result for the presence of these bound antibodies. This is particularly important in clinical settings for diagnosing conditions such as autoimmune hemolytic anemia, hemolytic disease of the newborn, or transfusion reactions.

In contrast, the other options focus on different aspects of blood bank testing:

• Mediating hemolysis of indicator red blood cells is not the main goal of this test; rather, it is more about detecting their presence through agglutination.

• Precipitating anti-erythrocyte antibodies does not accurately describe the action of the antiglobulin reagent, which is meant to bind to these antibodies on the