Which test result would most strongly support immune-mediated hemolytic anemia?

• A. Negative Coombs test
• B. Microcytosis without reticulocytosis
• C. Positive Coombs test
• D. Low bilirubin

Answer: (C)

In immune-mediated hemolytic anemia, the immune system marks red blood cells with antibodies or complement, leading to their destruction. The direct Coombs test (direct antiglobulin test) detects these antibodies or complement bound to the surface of circulating erythrocytes. A positive result means there are immune components attached to red blood cells, which is strong evidence that the anemia is immune-mediated.

Negative Coombs would not support IMHA, since it shows no detectable antibody/complement on red cells. Microcytosis without reticulocytosis suggests other issues like iron deficiency, and IMHA typically elicits a regenerative response with reticulocytosis. Low bilirubin is not supportive of hemolysis, where bilirubin from red cell breakdown is usually elevated. Therefore, the positive Coombs test best fits immune-mediated destruction.