[Aggregative behavior and calcium content of platelets in thrombocythemia and thrombocytosis].

Patients with thrombocythaemia due to myeloproliferative disorders (n = 21), with secondary thrombocytosis of various origin (n = 16), and a control group of healthy donors (n = 20) were investigated with respect to the aggregation behaviour and the total calcium content of blood platelets. The calcium content was significantly lower in both groups of patients as compared to controls (2 p less than 0.001). In 16 of 21 patients with myeloproliferative disorders platelet rich plasma did not respond to epinephrine (15 mumol/l), a concentration which induced at least weak aggregation in 14 of 16 patients with secondary thrombocytosis and also in healthy subjects. In patients with thrombocythaemia the mean extent of aggregation induced by epinephrine, collagen or adenosin diphosphate was significantly lower as compared to controls (2 p less than 0.001).