Clinical Information

Haptoglobin is a protein synthesized in the liver that binds with the globin α-chains in hemoglobin A, F, S, or C. Haptoglobin does not bind methemoglobin, heme, or unusual forms of hemoglobin in which the α-chain is missing. The haptoglobin-hemoglobin complex is rapidly removed from circulation by the reticuloendothelial system to prevent/minimize hemoglobin loss and to conserve iron. Indications for haptoglobin quantitation include anemia or other indicators of hemolysis, pregnancy induced hypertension, transfusion reactions (assay of pre- and post-transfusion samples), assessment of acute phase response and evaluation of changes in the α2-region of serum protein electrophoresis.

Decreased levels of haptoglobin are most frequently associated with conditions of increased intravascular hemolysis or hemoglobin turnover, such as hemolytic anemias, intravascular hemolytic transfusion reactions and malaria. Extravascular hemolysis does not usually affect haptoglobin concentrations. Other conditions with decreased haptoglobin levels include severe liver disease, vigorous athletic activity and mechanical heart valves where repetitive erythrocytic damage occurs. Elevated levels of haptoglobin are frequently associated with acute phase reactions (surgery, trauma, necrosis). Corticosteroid therapy and biliary obstructions can also increase haptoglobin levels.