A blood sample taken from a vein in your arm
This test measures the amount of haptoglobin in the blood. Haptoglobin is a protein produced by the liver. Its purpose is to find and attach itself to free haemoglobin in the blood. This forms a complex that is rapidly removed from the circulation by the liver and the iron is then recycled. Haemoglobin is a protein that transports oxygen throughout the body. It is normally found inside red blood cells (RBCs); very little is found free, except when RBCs are destroyed and their haemoglobin is released. When large numbers of RBCs are destroyed, haptoglobin concentrations in the blood will temporarily decrease as the consumption of haptoglobin exceeds that produced by the liver.
Increased RBC destruction may be due to inherited or acquired conditions that cause haemolysis of RBCs. Causes of haemolysis include: transfusion reactions, certain drugs, and/or mechanical breakage, such as may be seen with some artificial heart valves. Acquired haemolysis may also result from dysregulation of the immune system causing the body to destroy its own cells. The destruction may be mild or severe, acute or chronic, and it can lead to haemolytic anaemia. Patients with haemolytic anaemia may experience symptoms such as tiredness, weakness, and shortness of breath and their skin may be pale or jaundiced.
Liver disease may also result in low haptoglobin levels as liver damage may reduce both the production of haptoglobin and the removal of the haptoglobin-haemoglobin complexes.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
When is it requested?
The haptoglobin test may be requested if you have symptoms and signs of anaemia, such as paleness and weakness, along with findings suggestive of haemolytic anaemia, such as jaundice and dark urine. The test may be used with a reticulocyte count and a blood film when you have an abnormally low RBC count, haemoglobin, and/or haematocrit test result. It may also be used with a direct antiglobulin test when you have had a blood transfusion and are suspected of having a transfusion reaction or to investigate a suspected autoimmune haemolytic anaemia. The doctor may also request the test alongside a total or indirect bilirubin test.
What does the test result mean?
When haptoglobin levels are decreased, along with an increased reticulocyte count and a decreased RBC count, haemoglobin, and haematocrit, then it is likely that you have some degree of haemolytic anaemia.
If the haptoglobin is normal and the reticulocyte is increased, then RBC destruction may be occurring in organs such as the spleen and liver (called “extravascular” rather than “intravascular” haemolysis). Because the freed haemoglobin is not released into the bloodstream, the haptoglobin is not consumed and so is normal.
If the haptoglobin levels are normal and the reticulocyte count is not increased, then it is likely that the anaemia present is not due to RBC breakdown.
If haptoglobin levels are low without any signs of haemolytic anaemia, then it is possible that the liver is not producing adequate amounts of haptoglobin.
Is there anything else I should know?
Haptoglobin is an “acute-phase” protein; this means that it will be increased 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 used to help diagnose or monitor these conditions.
Drugs that can increase haptoglobin levels include androgens and corticosteroids such as prednisolone. Drugs that can decrease haptoglobin concentrations include isoniazid, quinidine, streptomycin, and birth control pills.
If haptoglobin levels are decreased, when will they return to normal?
It depends on the cause of the decrease. If it is due to acute haemolysis, such as may be seen with a transfusion reaction, then it will return to normal once the donor blood has been cleared from the system. If it is due to chronic haemolysis, then the levels should return to normal levels if the underlying condition can be treated. If the underlying condition cannot be treated or if the decreased levels of haptoglobin are due to reduced production due to liver disease, then levels may continue to be lower than normal.