Serum thrombocytopoietic activity in thrombocytopenias.

By means of a bioassay performed in rats utilizing 75Se-selenomethionine as a platelet marker in vivo, serum thrombocytopoietic activity (STA) was determined in 9 healthy volunteers and in 82 patients with thrombocytopenia, viz. 27 cases of ITP (9 acute and 18 chronic), 19 of aplastic anaemia, 19 of acute leukaemia and 17 of chronic proliferative disorders. STA was the highest in the ITP group (p less than 0.01), particularly in the cases of short duration (p less than 0.001). In acute leukaemia, the STA was remarkably elevated (p less than 0.02) and a negative correlation between STA and blood platelet count could be demonstrated. A negative correlation between STA and the duration of thrombocytopenia was also found in the patients with ITP. No significant increase of STA was observed in patients with ITP after corticosteroid administration. In 5 out of 7 cases who responded satisfactorily to splenectomy a significant fall of STA was demonstrated after surgery. A slight, but statistically significant, rise of the STA value was found in patients with aplastic anaemia (p less than 0.05). No STA elevation was observed in the cases of chronic proliferative disorders with thrombocytopenia.