What does a positive direct antiglobulin test (DAT) indicate?

A positive direct antiglobulin test (DAT) indicates the presence of antibodies that are bound to the patient's red blood cells. This test is primarily used to detect immune-mediated hemolytic anemias. In conditions such as autoimmune hemolytic anemia, the body produces antibodies against its own red blood cells, resulting in these antibodies being detected by the DAT.

When the test is performed, a reagent containing anti-human globulin is added to the patient's red blood cells. If antibodies or complement proteins are attached to the red blood cells, they will agglutinate in the presence of the reagent, leading to a positive result. This finding is crucial because it suggests that the hemolytic process is due to the immune system attacking the erythrocytes, which is vital information for further diagnostics and treatment.

The other options do not specifically relate to the purpose of the DAT. For example, while antibodies in serum might be tested in other assessments, they do not indicate the direct interaction with red blood cells that the DAT measures. A history of blood transfusion might explain the immune response but does not directly correlate with the result of a DAT. Lastly, adequate iron levels pertain to overall blood health and anemia status, but again, it does not