The mechanisms contributing to thromboembolic complications in children with acute lymphoblastic leukemia (ALL) are complex, but it is believed that two factors are of critical importance, i.e. increased thrombin generation and decreased antithrombotic potential of the blood plasma. We evaluated generation of thrombin in three periods of observation of the children: a) prior to chemotherapy, b) after remission-inducing chemotherapy, and c) after infusion of L-asparaginase in the consolidation phase. The study group consisted of 23 children (x = 6.8 years of age), and a control group of 11 children (x = 7.3 years of age). Thrombin-antithrombin III complex (TAT) was selected as a marker of thrombin generation and it was measured by ELISA method. TAT levels prior to chemotherapy were found to be normal in a small subgroup of children (7/23 - ca 30%), i.e. they were within the control range (1.5-4.5 µg/l), but all the levels increased following remission-inducing chemotherapy. In contrast, in the major subgroup of children whose TAT levels were elevated at presentation (16/23 - ca 70%) no significant changes were observed following chemotherapy. Conclusion: There is a subgroup of children with ALL whose thrombin generation is normal as measured by its marker - thrombinantithrombin III (TAT). Only in those children thrombin generation increases following chemotherapy.

Keywords: thrombin generation, thrombin-antithrombin III complexes, acute lymphoblastic leukemia