Four-fold staining including CD45 gating improves the sensitivity of multiparameter flow cytometric assessment of minimal residual disease in patients with acute myeloid leukemia.

Multiparameter flow cytometry (MFC) is capable of quantifying minimal residual disease (MRD) in acute myeloid leukemia (AML). Its broad application, however, is limited by a lack of sensitivity in about 20% of patients. CD45 gating may improve sensitivity. A broad panel of four-fold combinations of monoclonal antibodies including CD45 in each was used to define leukemia-associated aberrant immunophenotypes (LAIP), to define their sensitivities in normal bone marrow samples, and to compare results to data obtained without CD45 gating using triple staining. In 45 patients, a LAIP was defined, 11 normal bone marrow samples were analyzed as controls. The median percentage of LAIP-positive AML cells with and without CD45 gating was 21.95% (range, 3.31-82.52%) and 20.52% (range, 3.22-81.94%). The median percentage of LAIP-positive normal bone marrow cells ranged from 0.01 to 0.42% (median, 0.02%) and 0.02 to 0.58% (median, 0.15%) with and without CD45 gating. The difference of LAIP-positive cells between AML and normal bone marrow samples amounted to a median of 3.08 log (range, 1.22-4.01) and 2.28 log (range, 1.12-3.34) with and without CD45 gating. CD45 gating improves the sensitivity of MFC-based MRD monitoring in AML by 1 log.