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Haptoglobin

Definition

Haptoglobin is a protein produced by the liver. It connects to a certain type of hemoglobin in the blood.

A blood test can tell how much haptoglobin you have in your blood.

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

Your doctor may tell you to stop taking any drugs that can affect the test results.

Drugs that can raise haptoglobin levels include:

• Androgens
• Corticosteroids

Drugs that can lower haptoglobin levels include:

• Birth control pills
• Chlorpromazine
• Diphenhydramine
• Indomethacin
• Isoniazid
• Nitrofurantoin
• Quinidine
• Streptomycin

Never stop taking any medicine without first talking to your doctor.

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

This test is done to see how fast your red blood cells are destroyed. When red blood cells die, they release hemoglobin.

Haptoglobin attaches to this released hemoglobin, which is also called "free" hemoglobin. Free hemoglobin is not contained within red blood cells. The level of free hemoglobin is usually very low, but it rises whenever red blood cells are dying.

When the haptoglobin and hemoglobin attach, the new molecule goes to the liver, where parts of it (such as iron and amino acids) are recycled. The haptoglobin is destroyed.

When red blood cells are actively being destroyed, haptoglobin disappears faster than it is created. Thus, the levels of haptoglobin in the blood drop.

Normal Values

The normal range is 41–165 mg/dL (milligrams per deciliter).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher-than-normal levels may be due to:

• Acute rheumatic disease
• Biliary obstruction
• Peptic ulcer
• Ulcerative colitis
• Other inflammatory conditions

Lower-than-normal levels may be due to:

• Chronic liver disease
• Drug-induced immune hemolytic anemia
• Erythroblastosis fetalis
• Hematoma
• Hemolytic anemia due to G6PD deficiency
• Idiopathic autoimmune hemolytic anemia
• Immune hemolytic anemia
• Primary liver disease
• Transfusion reaction

What the risks are

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Schwartz RS. Autoimmune and intravascular hemolytic anemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 164.

Yee DL, Bollard CM, Geaghan SM. Appendix: Normal Blood Values: Selected Reference Values for Neonatal, Pediatric, And Adult Populations. In: Hoffman R, Benz EJ, Shattil SS, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 164.