What type of transfusion reaction would likely occur 8 days after a hemolytic reaction?

A transfusion reaction occurring 8 days after the initial transfusion is classified as a delayed immunologic reaction. This type of reaction is often associated with an anamnestic response, where the immune system is able to respond more robustly to previously encountered antigens due to memory B cells that have been activated by a prior exposure.

In this scenario, the presence of antibodies formed against donor red blood cell antigens can lead to hemolysis when the recipient is subsequently exposed to these antigens again, whether through another transfusion or through other exposure such as pregnancy or organ transplantation. The timing (8 days) aligns with typical delayed hemolytic reactions, which often result from secondary responses to sensitized antigens.

This reaction is different from immediate reactions, which can occur within minutes to hours post-transfusion and are commonly associated with clerical errors or acute hemolytic reactions. Delayed nonimmunologic reactions related to iron overload typically take much longer or are associated with multiple transfusions over time. Thus, the nature of the immune response and the timing indicates that a delayed immunologic reaction due to an antibody is the most likely scenario.