White blood cell differential counts in severely leukopenic samples: a comparative analysis of different solutions available in modern laboratory hematology

BACKGROUND: We evaluated the efficacy of white blood cell (WBC) differential counts in severely leukopenic samples by the Hematoflow method and by automated hematology analyzers and compared the results with manual counts. METHODS: EDTA-anticoagulated blood samples (175 samples) with WBC counts of 40-990/µL were selected. Hematoflow differential counts were performed in duplicates employing flow cytometry using the CytoDiff reagent and analysis software. Differential counts were also performed using the DxH 800 (Beckman Coulter) and XE-2100 (Sysmex) automated hematology analyzers. The sum of the manual counts by a hematology technician and a resident were used as the manual counts. RESULTS: The total analysis time and hands-on time required by the Hematoflow method were shorter than those required by manual counting. Hematoflow counts were reproducible, showed a good correlation with automated analyzers, and also showed strong correlation with manual counts (r > 0.8) in neutrophils, lymphocytes, and monocytes. None of the cases containing less than 4% blasts as analyzed by the Hematoflow method had blasts in the manual counts, but 8 cases of 21 cases (38.1%) with over 4% blasts by Hematoflow had blasts in manual counts. CONCLUSION: Hematoflow counts of severely leukopenic samples were reproducible and showed a good correlation with manual counts in terms of neutrophil, lymphocyte, and monocyte counts. The Hematoflow method also detected the presence of blasts. Manual slide review is recommended when over 4% blasts are found by Hematoflow.