A probabilistic approach for the evaluation of minimal residual disease by multiparameter flow cytometry in leukemic B‐cell chronic lymphoproliferative disorders

Abstract

Multiparameter flow cytometry has become an essential tool for monitoring response to therapy in hematological malignancies, including B‐cell chronic lymphoproliferative disorders (B‐CLPD). However, depending on the expertise of the operator minimal residual disease (MRD) can be misidentified, given that data analysis is based on the definition of expert‐based bidimensional plots, where an operator selects the subpopulations of interest. Here, we propose and evaluate a probabilistic approach based on pattern classification tools and the Bayes theorem, for automated analysis of flow cytometry data from a group of 50 B‐CLPD versus normal peripheral blood B‐cells under MRD conditions, with the aim of reducing operator‐associated subjectivity. The proposed approach provided a tool for MRD detection in B‐CLPD by flow cytometry with a sensitivity of ≤8 × 10⁻⁵ (median of ≤2 × 10⁻⁷). Furthermore, in 86% of B‐CLPD cases tested, no events corresponding to normal B‐cells were wrongly identified as belonging to the neoplastic B‐cell population at a level of ≤10⁻⁷. Thus, this approach based on the search for minimal numbers of neoplastic B‐cells similar to those detected at diagnosis could potentially be applied with both a high sensitivity and specificity to investigate for the presence of MRD in virtually all B‐CLPD. Further studies evaluating its efficiency in larger series of patients, where reactive conditions and non‐neoplastic disorders are also included, are required to confirm these results. © 2008 International Society for Advancement of Cytometry