What is haptoglobin?

Haptoglobin (sometimes abbreviated as Hp) is a glycoprotein that is produced by the liver in our bodies. Haptoglobin is also the protein that is encoded by the HP gene in humans. In blood plasma, haptoglobin function is to bind free hemoglobin present in the blood, which is released from erythrocytes with high affinity and thereby inhibits its oxidative activity. Then the haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system, mostly the spleen. In clinical settings the haptoglobulin assay is used to monitor and screen for intravascular hemolytic anemia. In intravascular hemolysis, free hemoglobin will be released into circulation and hence haptoglobin will bind the hemoglobin. In case of intravascular hemolysis, in which there is an increase in the release of hemoglobin in the blood, haptoglobin therefore is called upon to retrieve it and bring it back to the liver. However haptoglobin is not a reliable way to differentiate between intravascular and extravascular hemolysis.

This genes function is to encode a preproprotein to yield both alpha and beta chains, which as a matter of fact combine as a tetramer to produce haptoglobin. Haptoglobin functions to bind free plasma hemoglobin, which allows degradative enzymes to gain access to the hemoglobin while at the same time preventing loss of iron through the kidneys and protecting the kidneys from damage by hemoglobin. Haptoglobin is mostly produced by the hepatcoytes, but it can also be produced by other tissues of the body such as the lung, kidney and skin.


Why measure the level of haptoglobin?

The examination to measure the level of haptoglobin may be useful in the processes of monitoring hemolytic anemia. Decreased values can also indicate a slower type of red cell destruction unrelated to anemia. For example, destruction can be caused by mechanical heart valves or abnormal hemoglobin, such as sickle cell disease or thalassemia. Haptoglobin is known as an acute phase reactant. Its level increases during acute conditions such as infection, injury, tissue destruction, some cancers, burns, surgery, or trauma. Its purpose is to remove damaged cells and debris and rescue important material such as iron. Haptoglobin levels can be used to monitor the course of these conditions.

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


Standard of preparation

Sampling is usually done in the morning, when you visit the hospital. Fasting prior to the examination is required, and will be coordinated by the doctor. It is also important to inform the doctor of any current medication you are taking as it may affect the results of the examination. Drugs that may raise haptoglobin levels are, Androgens and Corticosteroids. However drugs that may lover the levels of haptoglobin are, isoniazid, nitrofurantoin, birth control pills, chlorpromazine, quinidine, streptomycin, diphenhydramine and indomethacin. Do not stop taking these medications prior to meeting the doctor, who will then recommend further steps. Prior medical history may be needed if the doctor requires it.


Is the exam painful or dangerous?

The examination is neither painful nor dangerous. The patient may feel a slight tingling sensation, when the needle enters the arm.


How is the exam performed?

The exam is done by a simple blood test.