Clinically, haptoglobin measurement can be a sensitive indicator of acute phase reactions and hemolytic disorders. A decreased level is indicative of intravascular hemolysis. Haptoglobin forms a complex with free hemoglobin released from damaged erythrocytes. DECREASES in haptoglobin are seen most frequently in the following conditions: hemolytic anemias (secondary to autoantibodies), alloantibodies, RBC membrane or enzyme defects, hemoglobinopathies (mechanical, parasitic or bacterially induced), acute hepatitis (poor prognosis), severe liver damage, cirrhosis, cholestasis, hepatitis, subacute bacterial endocarditis, renal infarction, blood transfusion, infectious mononucleosis, and congenital ahaptoglobinemia. INCREASES in haptoglobin may be seen in any acute phase response to necrotic inflammatory disease or during steroid therapy.