[Differential diagnosis of primary and secondary erythrocytosis by means of in vitro culture of hematopoietic stem cells].

Peripheral blood precursor cells from all of 12 patients with polycythaemia vera (PV) formed hemoglobinized colonies in vitro without addition os was strictly epo-dependent in 30 normals and 8 patients with erythrocytosis of other origin. By addition of 1 U epo/ml to the cultures, colony formation was increased up to 5-fold in PV. Untreated patients with a short history had the highest numbers of such epo-responsive precursor cells. In 3 patients with concomitant myelofibrosis, erythroid in vitro growth was abundant, but scattered, single colonies could hardly be identified and their hemoglobinization was poor. This picture did not change with addition of epo, and hemoglobinization did not improve. In vitro grown colonies in PV had morphological abnormalities as compared to colonies grown from normal precursor cells: all stages of erythroid differentiation and up to 50% necrotic cells were found within single colonies. Scattered colonies contained an excess of large, immature, vacuolated erythroblasts. It is concluded that these functionaland morphological abnormalities of in-vitro erythropoiesis are a reliable indicator of PV. Further, transition to myelofibrosis is recognized by a characteristic growth pattern with decreased epo-responsiveness.