The hormone EPO is necessary for the proper RBC production and is made by the kidneys. The level of this hormone varies inversely with respect to hematocrit. This test is used as a method to differentiate between primary and secondary Polycythemia. The primary Polycythemia is caused by High altitude, pulmonary diseases and tobacco use whereas the second one occurs due to tumours. The test is pretty useful in finding the candidates who need to undergo EPO replacement therapy and can also be used to diagnose patients who are undergoing the therapy to find if the therapy is working or not.
