Comparison of the Sysmex XT-2000iV and microscopic bone marrow differential counts in Wistar rats treated with cyclophosphamide, erythropoietin, or serial phlebotomy

Background In a previous study, it was demonstrated that bone marrow analysis using the Sysmex XT-2000iV hematology analyzer produced differential counts in untreated rats that were comparable to microscopic differential counts. Objective The aim of this study was to modulate hematopoiesis in rats in vivo either through pharmacologic treatment or serial phlebotomy, and to determine whether the Sysmex XT-2000iV could accurately analyze bone marrow quantitative changes when compared with results obtained by microscopy. Methods Rats were treated once with 0, 5, 20, and 40mg/kg cyclophosphamide (CP), 0, 50, 100IU/kg erythropoietin (EPO) on 4 consecutive days, or serial phlebotomy of 1-2mL of blood for 4days. Modulation of hematopoietic populations in bone marrow was evaluated using the Sysmex XT-2000iV hematology analyzer, and compared with microscopic differential counts. Results Correlation coefficients between M:E ratios determined by Sysmex and the microscopic method were 0.94, 0.96, and 0.98 for CP, EPO, or serial phlebotomy treatments, respectively. Mean concordance correlation coefficients for M:E demonstrated method agreement of 0.63, 0.92, and 0.85 for the 3 treatments. Quantitative automated and microscopic bone marrow differential counts were within the expected 95% confidence intervals for CP, EPO or serial phlebotomy. Conclusions The Sysmex XT-2000iV provides quantitative bone marrow differential counts of bone marrow cell series in rats with treatment-induced changes which are comparable to microscopic differential counts. Reliable automatic bone marrow differential counting allows increased throughput, sensitivity, reproducibility, and enhanced interpretation of bone marrow evaluation in rodent preclinical studies.