EPO and polycythemia: A low EPO level (2.9 mU/mL) has a specificity of 92% and sensitivity of 64% for the diagnosis of polycythemia vera; on the contrary, a high EPO level (>15.1 mU/mL) has a specificity of 98% and a sensitivity of 47% for the diagnosis of secondary polycythemia in a cohort study of 125 patients [8].