Question: What is (are) Polycythemia Vera ?
Answer: Key Points - Polycythemia vera is a disease in which too many red blood cells are made in the bone marrow. - Symptoms of polycythemia vera include headaches and a feeling of fullness below the ribs on the left side. - Special blood tests are used to diagnose polycythemia vera. Polycythemia vera is a disease in which too many red blood cells are made in the bone marrow. In polycythemia vera, the blood becomes thickened with too many red blood cells. The number of white blood cells and platelets may also increase. These extra blood cells may collect in the spleen and cause it to swell. The increased number of red blood cells, white blood cells, or platelets in the blood can cause bleeding problems and make clots form in blood vessels. This can increase the risk of stroke or heart attack. In patients who are older than 65 years or who have a history of blood clots, the risk of stroke or heart attack is higher. Patients also have an increased risk of acute myeloid leukemia or primary myelofibrosis.
Source: CancerGov

Question: How to diagnose Polycythemia Vera ?
Answer: Special blood tests are used to diagnose polycythemia vera. In addition to a complete blood count, bone marrow aspiration and biopsy, and cytogenetic analysis, a serum erythropoietin test is used to diagnose polycythemia vera. In this test, a sample of blood is checked for the level of erythropoietin (a hormone that stimulates new red blood cells to be made). In polycythemia vera, the erythropoietin level would be lower than normal because the body does not need to make more red blood cells.
Source: CancerGov