Serum deoxythymidine kinase correlates with peripheral lymphocyte thymidine uptake in chronic lymphocytic leukemia

The serum thymidine kinase (S‐TK) and proliferative activity of the leukemic cells were determined in 27 untreated patients with chronic lymphocytic leukemia (CLL). A significant positive correlation between S‐TK and proliferation expressed as a proliferative index (PI) was found (r = 0.70, p < 0.001). Additionally, PI (r = 0.59, p < 0.01) and S‐TK (r = 0.47, p < 0.05) correlated to peripheral blood lymphocyte count. When different variables and combinations of variables were studied in order to define their capacity for discriminating between progressive and indolent CLL, S‐TK activity and PI proved to be powerful indications. In longitudinal studies, both S‐TK and PI paralleled disease activity. A model where a combination of S‐TK and PI gives information of the degree of localized disease is proposed.