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. This evidence concerns the gene EPO and myeloproliferative disorder.