Validation of the Sysmex XN-V hematology analyzer for canine specimens

Abstract

Background: The Sysmex XN-V is derived from the new Sysmex XN series of human hematology analyzers. The main changes from the previously validated XT-2000iV analyzer include an optic-fluorescent analysis for platelets and nucleated RBC count.

Objective: We aimed to validate the Sysmex XN-V for canine blood according to American College for Veterinary Clinical Pathology and International Council for Standardization in Hematology recommendations.

Materials and methods: Canine EDTA blood specimens and quality control material were analyzed on the Sysmex XN-V to evaluate imprecision, bias, linearity, a comparison with the XT-2000iV analyzer, interference effects, carry-over, and stability. We also verified previously established Sysmex XT-2000iV reference intervals (RIs).

Results: Imprecision and bias were low (<5%) for most variables. Observed total error was lower than allowable total error for most measured variables except lymphocytes and monocytes. Visually determined linearity was excellent for all variables, except for lymphocytes. The correlation between the XN-V and XT-2000iV analyzers was high (>0.93) for all variables except MCHC and reticulocyte indices. Correlations between the Sysmex XN-V and manual differential counts were good for neutrophils and eosinophils, acceptable for lymphocytes, and fair for monocytes. Hemolysis, lipemia, and to a lesser extent icterus, had significant effects on measured hemoglobin concentration and associated variables. Carry-over was not visually observed for any variable. Changes in the Sysmex XN-V measurements after storage at 4℃ and 24℃ were similar to those described for the Sysmex XT-2000iV analyzer. The previously established Sysmex XT-2000iV RIs can be used to interpret results from the Sysmex XN-V analyzer for most variables except red blood cell distribution width and mean platelet volume.

Conclusions: The performance of the Sysmex XN-V analyzer was excellent and compared favorably with the Sysmex XT-2000iV analyzer.

Keywords: blood; comparison study; dog; method validation.

FIGURE 1

Cell identification comparisons on Sysmex XN‐V and the Sysmex XT‐2000iV scattergrams according to the manufacturer. WBC differential scattergrams (WDF and DIFF); WBC count scattergrams (WNR and WBC/BASO); reticulocyte scattergrams (RET(EXT) and RET); platelet scattergrams (PLT‐F and PLT‐O). B, basophils; D, debris; DIFF, WBC differential scattergram; L, lymphocytes; M, monocytes; mRBC, mature RBC; N, neutrophils; NRBC, nucleated red blood cells; P, platelets; PLT‐F, platelet scattergram with optic‐fluorescent analysis; PLT‐O, platelet scattergram with optic analysis; R, reticulocytes; RBC, red blood cells; RET, reticulocyte scattergram; RET(EXT), reticulocyte extended scattergram; W, WBC; WBC, white blood cells; WBC/BASO, WBC scattergram with the basophil channel; WDF, WBC differential; WNR, white cell nucleated

FIGURE 2

Measurements of canine RBC‐I, WBC, PLT‐F, and RET with the Sysmex XN‐V analyzer after dilution (concentration of undiluted specimen normalized to 1). PLT‐I, impedance platelet count; RBC‐I, impedance RBC count; RET, reticulocyte count

FIGURE 3

Passing‐Bablok plots (left) and difference diagrams (right) for RBC‐I, RET, WBC, and PLT‐I between the Sysmex XN‐V and Sysmex XT‐2000iV hematology analyzers. In the Passing‐Bablok plots, the thin gray line is identity (y = x); and the blue line is the regression curve with 95% confidence intervals. RBC‐I, impedance RBC count; PLT‐I, impedance platelet count; RET, reticulocyte count

FIGURE 4

WDF (A) and WNR (B) scattergrams from the Sysmex XN‐V analyzer for a canine blood specimen with a high percentage of band cells based on the manual differential count. (A) On the WDF scattergram, a well‐defined but extended population was observed at the neutrophils position and identified as neutrophils (turquoise dots) and lymphocytes (pink dots), despite a lack of cluster at the normal lymphocytes position. The WBC count was 32.3 × 10⁹ cells/L. The neutrophil percentages were 74.9% (XN) and 90.5% (manual; with 68.5% segmented neutrophils and 22% band cells); the lymphocytes percentages were 18.8% (XN) and 4.0% (manual); the monocytes percentages were 6.0% (XN) and 5.5% (manual); and the eosinophils percentages were 0.1% (XN) and 0.0% (manual). A flag was reported for neutrophils and lymphocytes, as well as an error message “WBC Abn Scattergram.” In this case, flag and/or error messages were also observed for PLT and RET. (B) WNR scattergram of the same dog. PLT, platelet count; RET, reticulocyte count; WDF, WBC differential; WNR, white cell nucleated

FIGURE 5

WDF (A), WNR (B), and RET‐EXT (C) scattergrams from the Sysmex XN‐V analyzer for a blood specimen from a dog with acute leukemia. (A) On the WDF scattergram, a large cloud is present at the location of the lymphocytes, neutrophils, and monocytes populations, and an arbitrary separation was performed by the analyzer (white arrow). (B) On the WNR scattergram, the cluster of leukocytes extended to the upper right part of the scattergram. (C) On the RET‐EXT scattergram, the reticulocyte clouds were characterized by a gap between mature reticulocytes (pink dots), and a population of high‐fluorescence particles (red and turquoise dots) suspected to be leukemic cells and not platelets (turquoise dots) or high‐fluorescence RET (red dots). The WBC count was 191.9 × 10⁹ cells/L. The neutrophil percentages were 0.0% (XN) and 4.5% (manual); the lymphocytes percentages were 66.1% (XN) and 0.0% (manual); the monocytes percentages were 33.1% (XN) and 2.0% (manual); and the eosinophils percentages were 0.0% (XN and manual). Blastic cells (93.5%) were only revealed by manual counting. A flag was reported for monocytes and lymphocytes results, as well as an error message “WBC Abn Scattergram”. In this case, flag and/or error messages were also observed for PLT and RET. PLT, platelet count; RET, reticulocyte count; RET(EXT), reticulocyte extended; WDF, WBC differential; WNR, white cell nucleated

FIGURE 6

Effects of hemolysis (blue), lipemia (orange), and icterus (gray) on canine RBC‐I, WBC, and PLT‐I and RET measurements with the Sysmex XN‐V (maximum concentrations of hemoglobin: 5 g/L; triglycerides: 10 g/L; bilirubin: 0.15 g/L; changes as % difference from native specimen); a, b, c: comparison with the native specimen using Dunnett's test, P <.05; 0.01; 0.001. PLT‐I, impedance platelet count; RBC‐I, impedance RBC count; RET, reticulocytes

FIGURE 7

Effects of carry‐over on RBC‐I, WBC, PLT‐F, and RET measurements with the Sysmex XN‐V (Five repeats of triplicates using the manufacturer's high and low control solutions). PLT‐F, fluorescence platelet count; RBC‐I, impedance RBC count; RET, reticulocytes