Relative and absolute polycythemia. How to tell them apart.

Relative and absolute polycythemia can be differentiated by measuring red cell mass and plasma volume. Often no treatment is recommended for patients with relative polycythemia unless directed toward vascular complications; phlebotomy is definitely contraindicated. For patients with polycythemia vera, however, phlebotomy is used routinely to decrease blood viscosity, while myelosuppression is reserved for patients who are not relieved by phlebotomy alone. Secondary polycythemia is controlled by correcting the cause or by circumspect use of phlebotomy if the cause cannot be remedied.