High and Low Haptoglobin: a test for the diagnosis of hemolytic anemia
Haptoglobin is a glycoprotein with a transport function that belongs to the category of alpha-2-globulins which is produced by the liver.
Its main function is to irreversibly bind the free hemoglobin circulating in the blood. The hemoglobin-haptoglobin complex thus formed is destined for degradation by the macrophages located in the liver and spleen which also have the task of providing for the recovery of the amino acids of which haptoglobin is made up and the iron present in haemoglobin.
The physiological function performed by haptoglobin is to provide for the replacement of our red blood cells as it allows on the one hand to recover the iron, on the other it provides for the removal from the circulation of now “aged” red blood cells with a process that takes the name of physiological haemolysis.
Under normal conditions, the concentration of haptoglobin is in equilibrium between hepatic synthesis and its elimination; if there is a reduction in the circulation then it means that there is an imbalance between synthesis and elimination in favor of the latter.
Furthermore, this protein also acts as an “acute phase protein” or that series of proteins that appear in the blood when there is an inflammatory process in progress.
Generally, the haptoglobin test is performed to detect the presence of hemolytic anemia or another type of anemia and can be useful to understand what is the cause that triggers the destruction of red blood cells.
How is it produced by our body?
Haptoglobin , also abbreviated HP, is a protein encoded by the HP gene in humans.
The main producers of this protein are the hepatocytes of the liver but other tissues are also able to produce it: skin, lung and kidney. In its simplest form, haptoglobin consists of two alpha chains and two beta chains linked together by disulfide bonds (bonds created between two thiol groups of cysteine).
The chains originate from a precursor protein which, following proteolytic cleavage, gives rise to the single protein chains. In the human population the Hp gene exists in two allelic forms: Hp1 and Hp2 and the latter arose due to the partial duplication of the former.
Normal values
The normal values of haptoglobin in both men and women are between 40-300 mg/dL and reach these values starting from the fourth month of life. I remind you that these values can change both according to the method used for the dosage and according to the laboratory.
Therefore, the values to be used as reference intervals are those present on the report.
When do values increase?
Blood levels of this protein may increase in the following cases:
- nephrotoxic syndrome;
- burns;
- both acute and chronic inflammation;
- infections of various origins;
- neoplasms with metastases although it has little value when considered in isolation. Your doctor will compare this value to other tumor markers .
When do they decrease?
The values of this protein can decrease as a result of liver problems, following the use of oral contraceptives and in the case of intravascular haemolysis and haemolytic anemia which involves a destruction of red blood cells.
This can be caused by:
- inherited diseases that cause abnormalities in the size and shape of red blood cells such as hereditary spherocytosis;
- spleen disorders;
- bone marrow pathologies;
- liver cirrhosis.
Hemolytic anemia is a very serious condition for the body because it causes an insufficient supply of oxygen to the tissues due to the progressive destruction of red blood cells.
The dosage of haptoglobin , therefore, is very important to evaluate the presence of this or other forms of anemia.
Low haptoglobin can be caused by an alteration in the gene that produces it or in one of its regulatory regions.
Gene alterations are linked to the onset of other diseases such as diabetic nephropathy, increased incidence of coronary heart disease in patients with type 1 diabetes, Crohn’s disease, primary sclerosing cholangitis, idiopathic Parkinson’s disease and protection from infection of Plasmodium falciparum responsible for malaria.
Why does the doctor recommend this analysis to us?
Generally, the reasons that lead the doctor to advise you to perform a haptoglobin test are based on the objective examination of some symptoms that you may experience in case of anemia. Among these we mention:
- always cold extremities;
- fatigue and dyspnea (difficulty breathing);
- White face;
- altered heart rate;
- dizziness;
- pain in the upper abdomen;
- jaundice.
The latter two symptoms are associated with liver damage, and jaundice, in particular, is caused by elevated levels of bilirubin in the blood .
Bilirubin is a pigment that is formed following the disposal of hemoglobin which is poured into the bloodstream following the destruction of red blood cells by the spleen. If the latter are destroyed at a rate greater than their production, it is possible that our body is unable to dispose of all the hemoglobin present.
What to know before the exam?
The test for the haptoglobin dosage does not require any special precautions. However, it is important to inform your doctor about your medical and family history as well as any use of medicines that could interfere with the exam.
In fact, pathologies such as rheumatoid arthritis, ulcerative colitis and liver disease as well as the use of cortisone and contraceptives can alter the result of the examination.
She defines herself as curious by nature. In 2006 she graduated with honors in Biotechnology at the Sapienza University of Rome. Between 2005 and 2009, she carried out a university internship and research activity in the field of tumor immunotherapy. She is a co-author of three scientific publications. Since 2007 you have associated your passion for science with that for the web, starting the management of the FitnessEquilibrium.com project.