Erythropoietin is not a routine test. It is ordered primarily to help differentiate between different types of anemia and to determine whether the amount of erythropoietin being produced is appropriate for the level of anemia present. It is usually ordered following abnormal findings on a complete blood count (CBC), a group of tests that includes a RBC count and evaluation, a hemoglobin, and a hematocrit. These tests establish the presence and severity of anemia and give the doctor clues as to the likely origin of the anemia. Erythropoietin is ordered to help determine if an insufficiency of the hormone may be causing and/or exacerbating the anemia.
In people with chronickidney disease, the test may be ordered at intervals to evaluate the kidneys' continued ability to produce sufficient erythropoietin. The erythropoietin test is not usually used as a monitoring tool for anemia. This is done by following the RBC count, hemoglobin, hematocrit, and reticulocyte count, a measurement of immature RBCs in the blood and an indicator of bone marrow function.
Occasionally, an erythropoietin test may be ordered to help determine if a condition that is causing an excess production of RBCs (polycythemia) is due to an overproduction of erythropoietin.
An erythropoietin test may be ordered when a person has anemia that does not appear to be caused by iron deficiency, vitamin B12 or folate deficiency, hemolysis, or by blood loss, such as that due to gastrointestinal bleeding. It may be ordered when the RBC count, hemoglobin, and hematocrit are decreased and the reticulocyte count is inappropriately normal or decreased. It is ordered when a doctor is attempting to distinguish between a condition that is suppressing bone marrow function and an insufficiency of erythropoietin.
If someone has chronickidney disease, erythropoietin levels may be ordered whenever the doctor suspects that kidney dysfunction could be interfering with erythropoietin production.
If a person has too many RBCs, an erythropoietin level may be ordered during an investigation of the overproduction to see if increased erythropoietin concentrations are present.
If erythropoietin levels are increased and someone is anemic but not producing a sufficient number of new RBCs, then the anemia is likely to be related to a decrease in bone marrow function. If a person is anemic and erythropoietin levels are low or normal, then the kidneys may not be producing an appropriate amount of the hormone.
If a person has too many RBCs and erythropoietin levels are increased, then it is likely that excess erythropoietin is being produced – either by the kidneys or by other tissues in the body. If there is excess RBC production and erythropoietin levels are normal or low, then it is likely that the polycythemia has a cause that is independent of erythropoietin production.
If anemia is due to a vitamin B12, folate, or iron deficiency, then the anemia may persist even when adequate amounts of erythropoietin are being produced. The RBCs produced in these deficiencies may not be normal in size, shape, and/or hemoglobin content. If someone is producing an abnormal form of hemoglobin, such as may occur with thalassemia, or has a bone marrow disorder, then increased erythropoietin may not resolve the anemia.
Those who are pregnant, who are chronic smokers, have lung disease, or who live at high altitudes may have increased levels of erythropoietin.
A synthetic form of erythropoietin (recombinant human erythropoietin or rh-EPO) has been developed to help increase RBC production in people with chronickidney disease and other anemias related to bone marrow suppression and/or failure, such as that due to radiation or chemotherapy treatment for cancer. The drug treatment, which is given intravenously or by subcutaneous injection, is expensive and its stimulation of the bone marrow lasts only a few hours. The synthetic hormone's use has been promising, helping to decrease the need for blood transfusions and improving the quality life for many affected people.
In March 2007, however, the FDA issued stronger safety warnings with regard to erythropoiesis-stimulating agents (ESAs). The public health advisory included revised product labeling and recommendations to monitor the health of those on ESAs, especially people with cancer or kidney disease. The safety information recommends that doctors monitor red cell levels (hemoglobin levels) and prescribe only the amount of ESA needed to stimulate the production of red cells to avoid blood transfusions. If some people are given higher than recommended doses, they run an increased risk of developing blood clots, heart attacks, strokes, and death. Also, certain people with cancer may experience a growth in tumor size.
The same synthetic erythropoietin is also being used by some athletes as a form of "blood doping." Those who use it are trying to increase their endurance and oxygen capacity by increasing the number of RBCs in their bloodstream. This use of the drug can be dangerous, resulting in hypertension and increasing the viscosity of the blood. Its use has been prohibited by most sports organizations, including the International Association of Athletics Federations, and erythropoietin is now being tested for as part of the Olympics anti-doping program.
This article was last reviewed on May 7, 2012. | This article was last modified on August 27, 2012.
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