Serum anti-platelet activity in acute leukemias (AL) and chronic thrombocytopenic purpura (ITP).

Serum anti-platelet activity in 44 patients with acute leukemia (AL), 19 patients with idiopathic thrombocytopenic purpura (ITP) and 30 healthy controls was studied by using the platelet factor 3 availability test (PF-3) and the inhibition test of clot retraction. Shortening of the clotting time in PF-3 test performed with isologous platelets was found in 30 of 44 cases as a result of accelerating the intrinsic coagulation pathway. During AL remission in 6 examined cases an effect of this serum activity on autologous platelets was demonstrated. Serum anti-platelet activity was inhibited by rabbit anti-IgG. The obtained results suggest that the activity present in the globulin fraction of AL patients serum may contribute to thrombocytopenia in this disease. The influence of various concentrations and combinations of cytostatics on PF-3 and the inhibition of clot retraction tests were examined in vitro. Out of vincristine, methotrexate, cytosine arabinoside and cerubidine only the combination of cytosine arabinoside and vincristine caused the clotting time in the PF-3 test to be shortened. As a single drug only methotrexate caused an inhibition of clot retraction.