Relationship of a leukemia-associated antigen to the presence of lymphoblasts in the peripheral blood in children with acute lymphocytic leukemia

Peripheral blood samples from 57 children with newly diagnosed E-rosette-negative, surface-immunoglobulin-negative acute lymphocytic leukemia (ALL) were studied for the presence of a leukemia-associated antigen (ALLA). Ficoll-Hypaque separated cells were tested using a rabbit antiserum to human null lymphoblasts and an indirect immunofluorescent assay. The percentage of ALLA-positive cells was compared to the percentage of lymphoblasts determined by differential counts of a Wright-Giemsa-stained smear of a concurrently obtained peripheral blood sample. The mean ratio of percentage of lymphoblasts to percentage of ALLA-positive cells was 0.90. However, in 13 patients, the ratio of percent of ALLA-positive cells to percent of lymphoblasts was equal to or greater than 2:1. In the blood of 6 additional children (5 newly diagnosed, 1 relapsed patient) in whom no morphologically identifiable lymphoblasts were detected, ALLA-positive cells were present (7%-49%). These results indicate that testing for ALLA-positive cells is a sensitive technique for detection of leukemic cells in children with ALLA-positive ALL.