Blood volume, erythrokinetics and spleen function in thrombocythaemia.

Essential thrombocythaemia was diagnosed in a series of 18 patients on the basis of platelet counts greater than 1,000 X 10(9)/1. Radionuclide studies have been carried out to distinguish thrombocythaemia as a primary disease from polycythaemia vera, myelofibrosis and chronic granulocytic leukaemia presenting with high platelet counts. These have included blood volume and spleen function, and radio-iron (52Fe) has been used to demonstrate the presence of extramedullary (splenic) erythropoiesis. The value of these investigations in distinguishing between the various myeloproliferative disorders associated with thrombocythaemia is illustrated.