Haptoglobin |
| Definition: |
| A test that measures the amount of haptoglobin, a protein that binds free hemoglobin, in blood. |
| How the test is performed: |
| Adult or child: Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. Infant or young child: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding. |
| How to prepare for the test: |
| The health care provider may advise you to withhold drugs that may affect the test (see "Special considerations"). Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
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| How the test will feel: |
| When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed: |
| Haptoglobin is measured as an indicator of the rate of red blood cell destruction (hemolysis). Haptoglobin is a protein that is secreted into the blood by the liver. This protein binds free hemoglobin. The concentration of "free" hemoglobin (that is, outside red blood cells) in plasma (the fluid portion of blood) is ordinarily very low. However, free hemoglobin is released when red blood cells hemolyze for any reason. After haptoglobin binds hemoglobin, it is taken up by the liver. The liver recycles the iron, heme, and amino acids contained in the hemoglobin protein. This process destroys haptoglobin as well as hemoglobin. In the presence of active hemolysis, the rate of haptoglobin destruction will outpace the rate at which new haptoglobin is created. Consequently, the concentration of haptoglobin in the blood will decrease. |
| Normal Values: |
| The normal range is 27 to 139 mg/dl. Note: mg/dl = milligrams per deciliter |
| What abnormal results mean: |
| The serum haptoglobin is most commonly used to detect intravascular destruction (hemolysis) of red blood cells. Greater-than-normal levels may indicate:
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| What the risks are: |
| Special considerations: |
| Haptoglobin levels maybe affected by the presence of liver disease (if the liver is unable to maintain its normal production of plasma proteins), kidney disease (if plasma proteins are lost in the urine), drugs that affect hepatic (liver) protein synthesis (creation of new proteins by the liver), extensive blood loss, and a variety of conditions that secondarily affect liver and kidney function. Drugs that can increase haptoglobin measurements include androgens and corticosteroids Drugs that can decrease haptoglobin measurements include chlorpromazine, diphenhydramine, indomethacin, isoniazid, nitrofurantoin, oral contraceptives (birth control pills), quinidine, and streptomycin. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
Reviewed By: Rebecca Elstrom, M.D., Division of Hematology-Oncology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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