In what condition would you expect a negative direct antiglobulin test but positive indirect antiglobulin test?

The scenario of having a negative direct antiglobulin test (DAT) while also showing a positive indirect antiglobulin test (IAT) is associated with conditions where the patient's immune system has produced antibodies that are not bound to red blood cells in circulation.

In the case of a delayed hemolytic reaction, which can occur after a blood transfusion, the antibodies that are formed in response to previously transfused blood group antigens often take time to develop. This means that in the initial phase after transfusion, the antibodies may not be present in a sufficient quantity or may not yet be attached to the patient's red blood cells, resulting in a negative DAT. The IAT, however, detects free antibodies in the serum, which would be present as the immune system recognizes and responds to the foreign antigens.

When considering options like warm autoimmune hemolytic anemia and cold agglutinin disease, these conditions typically result in a positive DAT due to the antibodies being bound to red blood cells, leading to agglutination and hemolysis. Acute hemolytic transfusion reactions often feature a positive DAT due to the immediate interaction of the transfused blood with pre-existing antibodies in the recipient, causing a direct reaction.

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