Usefulness of thresholds for smear review of neutropenic samples analyzed with a Sysmex XN-10 analyzer

Neutropenia is one of the main criteria for a blood smear review. The objective of this study was to compare the thresholds proposed by the international consensus group for hematology review (1.0 10⁹/L) and the French speaking Group for Cellular Haematology (1.5 10⁹/L) in terms of the number of useless smears. We collected 112,097 analyzed samples from four laboratories equipped with XN instruments (Sysmex, Kobe, Japan) during early 2016. The only exclusion criterion was a leucocyte count below 0.5 10⁹/L. In the absence of abnormal cells and/or morphology suggesting haematological disease, samples were classified as 'negative for morphology' and the differential from the XN-10 was reported. These smear procedures were considered as uninformative. Some 2202 samples met the criterion for neutropenia (<1.5 10⁹/L) for slide review representing 1.96% of the total. These included 1031 with neutropenia alone and 1171 neutropenia plus other abnormalities. Of the 1031 with neutropenia alone, 886 had a neutrophil count between 1.0 10⁹/L and 1.5 10⁹/L. The smear was uninformative for all of these samples. In conclusion, microscopic examination of a blood smear provided very limited information in cases of neutropenia without other abnormalities.