125I fibrinogen turnover in polycythaemia: the effect of phlebotomy.

Patients with polycythaemia vera and secondary polycythaemia studied with 125I-labelled fibrinogen, had a significantly increased plasma fibrinogen turnover. The abnormalities were greater in polycythaemia vera and correlated with platelet count but not with packed cell volume. In six patients with polycythaemia vera, phlebotomy reduced the packed cell volume to 0.46 or less. Although fibrinogen turnover decreased significantly in all patients, it remained outside the normal range in four cases. The concept of a prothrombotic state is discussed, and also the importance of these observations with respect to various forms of treatment.