Erythropoietin
The Test
How is it used?
In patients with chronic kidney 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 is due to an overproduction of erythropoietin.
When is it ordered?
If you have chronic kidney disease, erythropoietin levels may be ordered whenever your doctor suspects that kidney dysfunction could be interfering with erythropoietin production.
If you have too many RBCs, an erythropoietin level may be ordered during an investigation of the overproduction to see if increased erythropoietin concentrations are present.
What does the test result mean?
If you have 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 tissue in your body. If you have 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.
Is there anything else I should know?
A synthetic form of erythropoietin (recombinant human erythropoietin or rh-EPO) has been developed to help increase RBC production in patients with chronic kidney 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 patients.
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 patients 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 patients are given higher than recommended doses, they run an increased risk of developing blood clots, heart attacks, strokes, and death. Also, certain cancer patients 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 (thickness) 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.
