Validation of Sysmex XT-2000iV analyzer-generated quantitative bone marrow differential counts in cynomolgus monkeys, Beagle dogs, and CD-1 mice.

Background In a previous study, the validation of rat bone marrow (BM) collection, processing, and analysis using the Sysmex XT-2000iV (Sysmex Corporation, Kobe, Japan) hematology analyzer showed that the Sysmex hematology analyzer produced BM differential counts that were comparable to those obtained with microscopic differential counts. Objective This study was conducted to expand the validation of the Sysmex TNCC (total nucleated cell count) and 5-part BM differential in cynomolgus monkeys, Beagle dogs, and CD-1 mice, which are alternate species that are also frequently used in preclinical safety studies. Methods The Sysmex 5-part BM differential counts were generated with a two-step process, whereby proliferating and maturing erythroid and myeloid cells were determined by preset gating and lymphocytes were determined using species-specific B- and T-lymphocyte antibodies and a magnetic cell-sorting method (MACS). Agreement with microscopic myelograms with 500-cell differential counts was determined from BM suspensions of 62 cynomolgus monkeys, 47 Beagle dogs, and 44 CD-1 mice. Results The correlation coefficients between methods for myeloid to erythroid (M:E) ratios in all three species was > 0.928. The Bland-Altman differences between methods were approximately +/- 0.3 units for the M:E ratio in dogs and mice, and +0.6 and -0.4 in monkeys. The upper limits of agreement for all three species were <= 7% for maturing myeloid cells, <= 6% for maturing erythroid cells, and <= 4% for proliferating myeloid cells, proliferating erythroid cells, and lymphocytes. Conclusions The Sysmex XT-2000iV produces an automated M:E ratio and a 5-part differential count equivalent to microscopic differential counts in cynomolgus monkeys, Beagle dogs, and CD-1 mice.