The autocontrol is used to detect the presence of autoantibodies against the patient’s own red blood cells. Which combination is used in the autocontrol?

• A. Donor serum plus donor red blood cells
• B. Patient serum plus patient red blood cells
• C. Donor serum plus patient red blood cells
• D. Patient serum plus donor red blood cells

Answer: (B)

Autocontrol tests for antibodies that react with the patient’s own red blood cells, so the patient’s serum is examined against their own cells. Using the patient’s own serum with their own red cells ensures that any autoantibody present will be detected against self antigens, reflecting what would happen in the patient. If this autocontrol is positive, it points to an autoantibody; if negative, any reactivity seen with donor cells during screening is more likely due to an alloantibody rather than an autoantibody. Other combinations would test antibodies in donor serum or against donor cells and would not reveal the presence of autoantibodies against the patient’s own cells. The correct combination is patient serum with patient red blood cells.