Which laboratory test confirms a suspected transfusion reaction?

• A. Skin testing
• B. Direct Coombs test
• C. White blood cell count
• D. C-reactive protein level

Answer: (B)

The finding you’re looking for in a suspected transfusion reaction is immune involvement of the red blood cells. The direct Coombs test specifically detects antibodies or complement attached to the patient’s red cells after a transfusion. If red cells are coated with IgG or C3, the test is positive, which supports an immune-mediated transfusion reaction such as an acute hemolytic reaction caused by incompatibility or alloantibodies.

Skin testing isn’t used to confirm hemolysis from a transfusion; it’s more about predicting allergic or anaphylactic reactions to transfusion components. A white blood cell count is a general measure that can be influenced by many conditions and isn’t specific to transfusion reactions. C-reactive protein is an inflammatory marker but does not confirm immune destruction of transfused red cells.