What does a positive direct antiglobulin test (DAT) indicate in the context of transfusion reactions?

What does a positive direct antiglobulin test (DAT) indicate in the context of transfusion reactions?

• A. DAT positivity indicates infection.
• B. DAT positivity is irrelevant to transfusion.
• C. DAT positivity indicates antibodies against recipient RBCs.
• D. DAT positivity indicates antibodies coating donor red cells or complement on donor red cells, consistent with transfusion reaction.

Answer: (D)

Direct antiglobulin test (DAT) detects immune proteins bound directly to red blood cells. In the setting of a transfusion, a positive DAT means that antibodies or complement are attached to donor red cells circulating in the recipient. This binding shows an immune-mediated process targeting the transfused cells, which is the core feature of a transfusion reaction such as an acute hemolytic event. It signals that donor red cells are being coated by antibodies or complement, leading to their destruction or clearance. This is not about infection, and it aligns with the immune mechanism behind transfusion reactions, rather than antibodies directed against the recipient’s own cells in isolation.

Direct antiglobulin test (DAT) detects immune proteins bound directly to red blood cells. In the setting of a transfusion, a positive DAT means that antibodies or complement are attached to donor red cells circulating in the recipient. This binding shows an immune-mediated process targeting the transfused cells, which is the core feature of a transfusion reaction such as an acute hemolytic event. It signals that donor red cells are being coated by antibodies or complement, leading to their destruction or clearance. This is not about infection, and it aligns with the immune mechanism behind transfusion reactions, rather than antibodies directed against the recipient’s own cells in isolation.