Terminal deoxynucleotidyl transferase activity in childhood leukemia.

The activity of terminal deoxynucleotidyl transferase (Tdt) was measured in mononuclear cells of 70 children with acute leukemia, in whom raised levels of Tdt were noted at diagnosis, relapse, or during remission. Serial measurements of Tdt activity were related to the percentage of blasts in the bone marrow and the clinical course of children both during therapy and after its completion. The Tdt values did not predict relapse in children with acute lymphoblastic leukemia nor did the quantitative determination correlate with the percentage of blasts in the bone marrow.