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Haptoglobin

Also known as: HPT; Hemoglobin-binding Protein; Hp
Formal name: Haptoglobin
Related tests: CBC; Reticulocyte count; Blood smear; Hemoglobin; Hematocrit; Bilirubin; Direct antiglobulin

The Test

How is it used?

Haptoglobin testing is used primarily to help detect and evaluate hemolytic anemia and to distinguish it from anemia due to other causes; however, it cannot be used to diagnose the cause of the hemolysis.

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When is it ordered?

The haptoglobin test is ordered when you have symptoms and signs of anemia, such as paleness and weakness, along with findings suggestive of hemolytic anemia, such as jaundice and dark urine. The test may be ordered along with a reticulocyte count and a blood smear when you have an abnormally low RBC count, hemoglobin, and/or hematocrit test result. It may also be ordered along with a direct antiglobulin test when you have had a blood transfusion and are suspected of having a transfusion reaction. The doctor may also order the test in conjunction with a total or indirect bilirubin test.

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What does the test result mean?

Looking for reference ranges?

When haptoglobin levels are decreased, along with an increased reticulocyte count and a decreased RBC count, hemoglobin, and hematocrit, then it is likely that you have some degree of hemolytic anemia.

If the haptoglobin is normal and the reticulocyte count is increased, then RBC destruction may be occurring in organs such as the spleen and liver. Because the freed hemoglobin is not released into the bloodstream, the haptoglobin is not consumed and so is normal.

If the haptoglobin concentrations are normal and the reticulocyte count is not increased, then it is likely that the anemia present is not due to RBC breakdown.

If haptoglobin levels are decreased without any signs of hemolytic anemia, then it is possible that the liver is not producing adequate amounts of haptoglobin.

 

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Is there anything else I should know?

Haptoglobin is considered an “acute-phase” protein; this means that it will be elevated in many inflammatory diseases, such as ulcerative colitis, acute rheumatic disease, heart attack, and severe infection. This can complicate the interpretation of the haptoglobin results. Haptoglobin testing is not generally used to help diagnose or monitor these conditions.

Haptoglobin levels may be affected by massive blood loss and by conditions associated with kidney dysfunction, as well as liver disease.

Drugs that can increase haptoglobin levels include androgens and corticosteroids. Drugs that can decrease haptoglobin concentrations include isoniazid, quinidine, streptomycin, and birth control pills.

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