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 40 mg/kg cyclophosphamide (CP), 0, 50, 100 IU/kg erythropoietin (EPO) on 4 consecutive days, or serial phlebotomy of 1-2 mL of blood for 4 days. 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.

Validation of Sysmex XT-2000iV generated quantitative bone marrow differential counts in untreated Wistar rats.

BACKGROUND: Preclinical drug trials frequently require assessment of bone marrow toxicity in animals to evaluate hematopoietic safety. Since the gold standard, cytologic evaluation, is time consuming and requires highly trained individuals, automated methods remain intriguing. OBJECTIVE: The Sysmex XT-2000iV hematology analyzer allows user-developed customizable gating. This study was conducted to validate the gating of bone marrow cell populations in Sysmex cytograms from untreated rats. METHODS: B- and T-lymphocytes and myeloid cells were experimentally depleted from Charles River Wistar Han IGS (CRL: WI [Han]) rat whole bone marrow suspension using a magnetic cell sorting (MACS) method. The positively and negatively selected populations were used to verify select gates within the Sysmex cytogram. Intra- and inter-animal precision, comparability between right and left femur, as well as agreement with microscopic myelograms based on 500 counted cells, were determined. RESULTS: Intra-sample precision and right-to-left femur comparability confirmed that gating was reproducible and stable. In 50 tested rats, myeloid to erythroid ratios (M:E) were 1.32 ± 0.33 in males and 1.38 ± 0.29 in females by Sysmex compared to 1.36 ± 0.32 in males and 1.42 ± 0.32 in females by microscopic evaluations. Bland-Altman differences between methods was ≤ ± 0.35 units for M:E, ≤ 5.4% for maturing myeloid cells, ≤ 3.4% for proliferating myeloid cells, ≤ 6.0% for maturing myeloid cells, ≤ 3.4% for proliferating myeloid cells, and ≤ 4.1% for lymphocytes. CONCLUSIONS: In untreated control Charles River Wistar Han IGS (CRL: WI [Han]) rats, the Sysmex XT-2000iV produced an automated M:E and 5-part differential count equivalent to microscopic differential counts.