Introduction: Differential counts of leukocytes are frequent, and often several automated blood cell counters are needed in contemporary laboratories. However, these modules are often individually quality assured. Our aim was therefore to validate the interchangeability of five hematology modules in a large modern laboratory and to compare them with our gold standard (GS) manual white blood cell differential count.Methods: At Copenhagen University Hospital, we compared five Sysmex XNmodules for neutrophils, lymphocytes, monocytes, eosinophils, basophils, and immature granulocytes (IG). We analyzed control samples in three levels to evaluate intra-and intermodular precision. Bias between modules was evaluated by analyzing 93 random patient samples within reference intervals. XN-modules' mean counts were compared with GS. Results:We found acceptable intramodular CV% (0.92%-8.76%), only neutrophils and eosinophils exceeded state-of-the-art imprecision or desirable specifications for medium control levels. Intermodular CV% showed significance difference for only monocytes (ANOVA, P < .0001). For patient samples, there were significant differences between XN-modules regarding four WBC types (ANOVA); however, proportional bias ranged from 1.7% to 3.8%, being within desirable specifications except basophils and IG (bias = 13.3% and 24.9%, respectively). Comparisons with GS, XNmodules exceeded desirable bias for basophils (lower than GS); monocytes and IG (higher than GS). Conclusion:This multimodule comparison shows acceptable intermodular imprecision and bias for clinical purposes, which is important for patient safety. Similar multimodule study should be performed with samples out of reference range in large-scale laboratories to confirm the interchangeability.

Increased mitotic activity in the bone marrow is a prerequisite to early-stage differentiated cells in the blood, and occurrence of circulating leukemic blast cells is characteristic for and indicates the existence of acute myeloid or lymphoid leukemia, but also other pathologies such as myelodysplastic syndromes or myeloproliferative neoplasms. 1,2 Malignant leukemia demands timely and correct drug management, which depends on accurate and valid bone marrow and peripheral blood analysis. 3 In the last decades,