Erythroid colony formation in primary proliferative polycythaemia, idiopathic erythrocytosis and secondary polycythaemia: sensitivity to erythropoietic stimulating factors.

This is a study of in vitro production of erythropoietic colonies from peripheral blood and bone marrow of normal subjects and patients with different polycythaemic conditions. Proliferative stimuli included: 1. Fetal calf serum (FCS) only. 2. FCS plus a source of erythropoietic-stimulating activity (ESA). 3. FCS + ESA + erythropoietin (Ep). It was found that normal subjects and patients with secondary polycythaemia (SP) exhibited full colony growth only in the presence of both ESA and Ep, while patients with primary proliferative polycythaemia (PPP) showed colony production with FCS alone, further enhanced in the presence of ESA and Ep. A group of patients with idiopathic erythrocytosis (IE), namely with an increase of red cell mass not accompanied by other signs of myeloproliferative disorder, and without underlying cause, showed a heterogeneous response to ESA which in some patients was significantly greater than in normal subjects or in SP patients. It appears therefore that sensitivity of erythropoietic colony formation to Ep and ESA may be helpful in differentiating among various forms of polycythaemia; this study also establishes the heterogenicity of the IE group.