Which test is used to detect antibodies attached to red blood cells?

The direct antiglobulin test (DAT) is specifically designed to detect antibodies that are already bound to red blood cells. This test is commonly used in blood transfusion and hemolytic disease of the newborn to identify whether there are antibodies present on the surface of red blood cells that could lead to their destruction.

The methodologies behind the test involve taking a sample of the patient’s red blood cells and mixing it with a reagent that contains antihuman globulin. If antibodies are present attached to the red blood cells, this reagent will bind to them and cause visible agglutination. This agglutination indicates a positive result, confirming that antibodies or complement components are indeed bound to the patient’s red blood cells.

In contrast, other tests listed, such as the indirect antiglobulin test, evaluate antibodies present in the serum rather than those that are already bound to cells. The hemagglutination test is a broader term that can refer to various methods of detecting virus-antibody interactions through red blood cells, and while the Coombs test is often used interchangeably with the direct antiglobulin test, it refers to a specific method of detecting both direct and indirect reactions.