Monocyte subset partitioning to distinguish CMML from other causes of monocytosis

Monocytosis is common and differentiating reactive causes from the myelodysplastic syndrome/myeloproliferative neoplasm chronic myelomonocytic leukaemia (CMML) can prove difficult for both pathologists and clinicians. Monocytes may be functionally and immunophenotypically divided into classical, intermediate and non-classical subtypes. There is growing evidence that elevated classical monocytes in peripheral blood may be a sensitive and specific indicator of CMML. Many of the antibodies used in monocyte partitioning have significant overlap with those used in peripheral blood T and NK cell assessment. The aim of this study was to confirm the efficacy of flow cytometry partitioning of monocyte subsets in distinguishing CMML from other causes of monocytosis. Furthermore, we aimed to assess the efficacy of a hybrid flow cytometry tube to allow for both monocyte and T/NK cell assessment in peripheral blood as a cost and time efficient method of analysing these cell compartments.