Polycythemia vera and other polycythemic states.

The diagnosis of polycythemia requires an accurate and independent assessment of both plasma volume and red blood cell mass. Patients with an increased red cell mass (absolute polycythemia) may be hypoxic or have an erythropoietin-secreting tumor or space-occupying lesion compressing the kidney. Those with a reduced plasma volume (relative polycythemia) most often are tobacco smokers, are taking diuretic or cardiac medications, or ingest increased quantities of caffeine-containing beverages. On the other hand, polycythemia vera is a systemic disease with multiple complications, which is best diagnosed through a complex of findings as outlined by the Polycythemia Vera Study Group.