What does a positive direct antiglobulin test (DAT) indicate in hemolytic anemia workup?

What does a positive direct antiglobulin test (DAT) indicate in hemolytic anemia workup?

• A. No hemolysis
• B. ABO incompatibility
• C. Antibodies or complement bound to red blood cells
• D. Absence of antibodies

Answer: (C)

A positive direct antiglobulin test means antibodies or complement are bound to the surface of red blood cells. The DAT, or direct Coombs test, detects in vivo coating of RBCs with IgG or C3 (complement) by using anti-human globulin to reveal those attached components after washing. In the hemolytic anemia workup, this indicates immune-mediated hemolysis, such as autoimmune hemolytic anemia or transfusion/drug-related hemolysis, where RBCs are targeted by antibodies or complement. If the test is negative, nonimmune causes of hemolysis are more likely.

A positive direct antiglobulin test means antibodies or complement are bound to the surface of red blood cells. The DAT, or direct Coombs test, detects in vivo coating of RBCs with IgG or C3 (complement) by using anti-human globulin to reveal those attached components after washing. In the hemolytic anemia workup, this indicates immune-mediated hemolysis, such as autoimmune hemolytic anemia or transfusion/drug-related hemolysis, where RBCs are targeted by antibodies or complement. If the test is negative, nonimmune causes of hemolysis are more likely.