What is the most common cause of an acute hemolytic transfusion reaction (AHTR)?

What is the most common cause of an acute hemolytic transfusion reaction (AHTR)?

• A. ABO incompatibility leading to intravascular hemolysis.
• B. Febrile nonhemolytic reaction due to donor cytokines.
• C. Allergic reaction to plasma proteins.
• D. Bacterial contamination of the transfusion unit.

Answer: (A)

The main idea is that acute hemolytic transfusion reactions are most commonly caused by ABO incompatibility, which triggers intravascular hemolysis. When donor red cells carry A or B antigens that the recipient has antibodies against (anti-A or anti-B), these IgM antibodies bind the cells and activate complement. This leads to rapid destruction of the transfused red cells inside blood vessels, releasing hemoglobin and causing symptoms such as fever, back or flank pain, hypotension, and potentially kidney injury or DIC. ABO antibodies are naturally occurring and typically present in high titers, making this the most frequent cause of AHTR. Other listed reactions describe different transfusion complications: febrile nonhemolytic reactions involve fever without genuine hemolysis from donor leukocytes or cytokines; allergic reactions to plasma proteins cause urticaria or anaphylaxis without hemolysis; bacterial contamination can cause septic transfusion reactions with fever and shock. But the hallmark intravascular hemolysis points to ABO incompatibility as the correct explanation.

The main idea is that acute hemolytic transfusion reactions are most commonly caused by ABO incompatibility, which triggers intravascular hemolysis. When donor red cells carry A or B antigens that the recipient has antibodies against (anti-A or anti-B), these IgM antibodies bind the cells and activate complement. This leads to rapid destruction of the transfused red cells inside blood vessels, releasing hemoglobin and causing symptoms such as fever, back or flank pain, hypotension, and potentially kidney injury or DIC. ABO antibodies are naturally occurring and typically present in high titers, making this the most frequent cause of AHTR. Other listed reactions describe different transfusion complications: febrile nonhemolytic reactions involve fever without genuine hemolysis from donor leukocytes or cytokines; allergic reactions to plasma proteins cause urticaria or anaphylaxis without hemolysis; bacterial contamination can cause septic transfusion reactions with fever and shock. But the hallmark intravascular hemolysis points to ABO incompatibility as the correct explanation.