EPO and polycythemia: The diagnostic workup includes: history, exclusion of other causes of erythrocytosis (cardiopulmonary disease, carbon monoxide poisoning, a myeloproliferative neoplasm, erythropoietin-producing tumor), pulse oxymetry measurement, hematology and biochemistry blood tests, normal or high serum erythropoietin (EPO) levels, low p50 value, HPLC electrophoresis, and genetic testing.