STANDARDIZED MULTICENTRIC QUANTIMETRY OF DIFFERENTIATION ANTIGENS EXPRESSION - THE GEILS APPROACH IN ACUTE LYMPHOBLASTIC-LEUKEMIA

The use of flow cytometry as a common tool has opened the field of qua ntimetric immunophenotyping. This could help refine the definition of leukemic proliferations, and perhaps provide new prognostic criteria. We investigated whether this approach could be applied to multicentric immunophenotyping. The reproducibility of quantitative measurements o n different types of flow cytometers was tested using a single batch o f calibrating and ''blind'' fluorescent beads. Less than 7% CV was obt ained between 20 different laboratories. We then explored the variatio ns noted with control or normal lymphocytes, using various CD4 monoclo nal antibodies, which were found to be lower than 10%. We finally appl ied this strategy to acute lymphoblastic leukemias (ALL), performing q uantitative measurements of CD10 using one single aliquoted batch of F ITC-CD10 in comparison with locally used reagents. PreB-ALL could inde ed be further stratified depending on the density of CD10 expression. Use of the same monoclonal antibody is however recommended, since PreB -ALL also seem to display epitopic variations of the CD10 molecule.