Which is not seen in Polycythemia Vera?

Polycythemia vera is characterized by an increase in red cell mass without any increase in level of erythropoietin. In fact erythropoietin level is decreased due to feedback by increased erythrocytes. The plasma erythropoetin level is a useful diagnostic test in patients with isolated erythrocytosis, because an elevated level excludes polycythemia vera as the cause for erythrocytosis.