Surveillance of Acute Leukemia by Multiparameter Flow Cytometry

The standard definition of remission in acute leukemia is the presence of less than 5% bone marrow blasts. However, even a much lower number of leukemic cells, referred to as “minimal residual disease” (MRD), may be associated with immediate relapse. Detection of MRD by means of immunocytological criteria is mainly hampered by the fact that no truly leukemic-specific antigen has been identified as yet. Thus, it is difficult to distinguish reliably between normal and leukemic blast cells, in particular when signs of bone marrow regeneration are present. In this study we attempted to overcome these obstacles by use of maker combinations and flow cytometric multiparameter analysis. We tried to explore to what extent acute leukemias could be monitored by this strategy and whether this approach is sensitive enough to predict relapse at an early stage.