American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the average onset time for signs and symptoms of delayed hemolytic transfusion reactions compared to acute reactions?

1. Quicker than acute reactions

2. Same as acute reactions

3. Slower than acute reactions

4. Variable with each case

The correct answer is: Slower than acute reactions

Delayed hemolytic transfusion reactions typically occur days to weeks after the transfusion, which is significantly slower than acute hemolytic reactions that generally manifest within minutes to hours. In a delayed reaction, the immune response involves the production of antibodies that were not initially present or were at a low level before the transfusion. As these antibodies develop and bind to transfused red blood cells, they lead to hemolysis, which can take time to become clinically apparent. The contrast in timing is essential for clinical recognition and management of these reactions. Understanding that delayed reactions have a slower onset allows healthcare professionals to monitor patients appropriately after transfusions and recognize that symptoms may arise at a later date, rather than immediately following the procedure. This knowledge helps in educating patients and planning follow-up assessments to catch any adverse events that may occur post-transfusion.