OBJECTIVETo evaluate the method and value of detecting bone marrow minimal residual disease (MRD) in B lineage acute lymphoblastic leukemia (B-ALL) by multiparameter flow cytometry (FCM).

METHODSThe FCM immunophenotyping of B-lymphocyte precursors in regenerating stage and MRD was analyzed by using two sets of 4-color antibody panels, including mainly CD34, CD10, CD45, CD19, in 26 regenerating bone marrow samples after chemotherapy and 297 consecutive bone marrow specimens from 50 patients with B-ALL, respectively. The immunophenotype of leukemia cells of B-ALL was also detected by four to six antibodies combination of 4-color CD45/SSC gating FCM. The CD19, CD10, CD34 fluorescence intensity of B-cell precursors in normal and leukemic bone marrow was compared by relatively quantitative method.

RESULTSTwelve patients were MRD positive (MRD(+)) among 50 patients during MRD monitoring, the percentages of residual leukemia cells were 0.06% to 7.73%. Eleven cases displayed CD45, CD34, CD19, CD10 antigens aberrant expression. Five patients were bone marrow relapsed and 4 of them were MRD (+) 7-17 weeks before relapse. The percentages of leukemia cells in all the 4 patients were over 0.1%. Only one patient relapsed with MRD negative. The regenerated B precursors could be divided into 3 stages according to the expression of CD45, CD34, CD19, CD10, CD22, and CD20 antigens. Abnormal expression of CD45, CD34, CD19, and CD10 were detected in 71.8% of 213 patients with B-ALL, the percentage of only aberrant expression of CD38 and myeloid antigen was 8.1%.

CONCLUSIONDetection of MRD by multiparameter flow cytometry is a rapid, quantitative and sensitive approach, and has a higher predictability for relapse.