Spontaneous erythroid colony formation in erythrocytosis.

Erythroid colony formation from the bone marrow and blood of 30 patients with erythrocytosis has been studied. Seventeen patients formed spontaneous erythroid colonies. They included patients with polycythaemia vera (PV) and 4 patients who did not quite fulfil the Polycythemia Vera Study Group criteria for PV, but had suggestive evidence of a myeloproliferative disorder. Thirteen patients did not form spontaneous colonies. They included patients with secondary polycythaemia, patients with normal total red cell volume and patients with absolute pure erythrocytosis of unknown origin. All patients with PV, and none with secondary polycythaemias, had spontaneous erythroid colony formation. Three of 4 untreated and 2 of 9 treated PV patients had increased number of CFU-E colonies in bone marrow. From these results it can be concluded that erythroid progenitor cell culture is a useful differential diagnostic method in erythrocytosis patients who cannot be classified clinically under PV or secondary polycythaemias.