This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Which is not seen in Polycythemia Vera? 
Select and explain. 
A. Ocular congestion, B. Increase RBC count, C. Increase erythropoietin level, D. Increased Vit B12 binding capacity
C: Increase erythropoietin level
Answer: C: Increase erythropoietin level 
Explanation: 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.