Mono-dysplasia score based on automated cell counter (Sysmex) – A novel parameter for differentiating reactive monocytosis from hematological malignancies

INTRODUCTION: In India, there is a high burden of infections such as tuberculosis, dengue, and malaria which are common causes of monocytosis. This increases the workload of smear examination by the pathologist. “Mono-dysplasia score” is obtained with a simple complete blood count on an automated cell counter and includes the parameters neutrophil (Ne) and monocyte (Mo) count and Ne-WX which is a Ne dispersion parameter. It is operator independent, objective, and does not require a high level of expertise.AIMS: The aims of the study were to assess the utility of Monoscore/mono-dysplasia score calculated using research parameters of Sysmex XN automated cell counter, as a screening tool for differentiating reactive monocytosis from hematological malignancies associated with monocytosis.MATERIALS AND METHODS: Samples sent in EDTA vacutainer for routine hemogram fulling the criteria for monocytosis (WHO criteria – absolute monocyte count ≥1 × 109/L and accounting for ≥10% of the total white blood cell count) were included in the study. Monoscore was calculated using the formula established by Schillinger et al. Flow cytometry, bone marrow examination, etc., were done as and when needed as standard-of-care tests to establish a final diagnosis.RESULTS: One thousand two hundred and fifty-seven samples were analyzed out of which 41 samples were chronic myelomonocytic leukemia and 126 were other hematological malignancies (HD) including acute leukemias, myelodysplastic syndrome, myeloproliferative neoplasm, etc. Using receiver operating characteristics curves, we established the cutoff 0.212 which showed a sensitivity of 97.6% and specificity of 96.4% to differentiated reactive monocytosis form HD.CONCLUSIONS: A sample showing monocytosis and Monoscore <0.212 and without any other flags can be safely auto-authorized without peripheral blood smears examination, reducing the burden of slides to be reviewed.