Objective:To investigate the value of normalization of flow cytometric blast counting in diagnosis of myelodysplastic syndrome(MDS).Methods:Multiple flow cytometric gating strategy was used to enumerate the number of CD16dim/-neutrophils and CD34+ cells.Normalization of bone marrow aspirates for hemodilution was performed according to the number of bone marrow CD16dim/-neutrophils,and then bone marrow CD34+ cells were re-enumerated.Diagnosis of 73 patients with MDS was performed according to the number of normalized CD34+ cells and compared with morphology.Results:The number of bone marrow CD16dim/-neutrophils was(50.33±17.52)% and(52.35±27.48)%(P0.05),and the number of bone marrow blasts by morphology was(0.43±0.64)% and(2.48±3.67)%(P0.01) respectively in control group and MDS group.The number of bone marrow CD34+ cells was(1.86±2.53)% and(3.24±4.02)%(P0.01) respectively before and after normalization in MDS group,which was significantly lower or higher than morphology counting respectively(P0.05),but the number of CD34+ cells in 63/73 patients whose level of CD16 expression in neutrophils was normal has no significant difference compared with those by morphology.And their diagnosis coincidence rate was 96.8%.Conclusions:The number of bone marrow CD16dim/-neutrophils can be used for normalization of bone marrow aspirates for hemodilution and the number of bone marrow CD34+ cells after normalization can be used for diagnosis of patients with MDS whose level of CD16 expression in neutrophils was normal.