What is being tested?
This test measures the amount of haptoglobin in the blood. Haptoglobin is a protein produced by the liver. Its job is to find and attach itself to free hemoglobin in the blood. This forms a complex that is rapidly cleared out of the circulation by transport back to the liver for destruction and recycling. Hemoglobin 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 hemoglobin released. When large numbers of RBC are destroyed, haptoglobin concentrations in the blood will temporarily decrease as the rate of use of haptoglobin exceeds the rate at which the liver can replace it.

Increased RBC destruction may be due to inherited conditions that cause abnormalities in the size, shape, or consistency of RBCs, an abnormal type of hemoglobin (hemoglobin variant), an acquired autoimmune reaction, a transfusion reaction, certain drugs, or mechanical breakage (such as may be seen with some prosthetic heart valves). The destruction may be mild or severe, acute or chronic, and it can lead to hemolytic anemia (a shortage of normal RBCs). Patients with hemolytic anemia may experience symptoms such as fatigue, weakness, and shortness of breath and their skin may be pale or jaundiced (yellowish).

Liver disease may also result in decreased haptoglobin concentrations as the liver damage may inhibit both the production of haptoglobin and the clearing of the haptoglobin-free hemoglobin complexes.

How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.