Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.
Vet Clin Pathol. 2021 Mar;50(1):28-36. doi: 10.1111/vcp.12981. Epub 2021 Mar 2.
The myeloperoxidase index (MPXI), on ADVIA hematology analyzers, reflects the mean neutrophil myeloperoxidase staining. It is used as a marker of inflammation in animals and people, but assay variability and storage stability are unknown.
We aimed to determine MPXI precision and stability with refrigerated storage of canine and equine EDTA-anticoagulated blood and compared MPXI results between two analyzers.
Inter-assay coefficients of variations (CVs) were determined from three human-based controls assayed before and after a 20- or 21-day calibration. Blood from 14-16 dogs and 26 horses was assayed 4-10 times within 1 day for intra-assay CV measurements. Median control and single run results from 18 canine and 35 equine samples were compared between analyzers. Blood from 10-12 dogs and 10-11 horses was analyzed after collection, and 24, 48, and 72 hours of refrigerated storage.
Inter-assay CVs of controls were 10.7%-15.9% and 6.4%-9.6% before and 4.3%-7.7% and 2.8%-17.5% after calibration, for ADVIA 1 and 2, respectively. Calibration altered peroxidase gain settings and improved precision. Intra-assay CVs were 0.6%-64% and 3%-350% for canine and equine samples, respectively. Median MPXI results differed significantly between the analyzers, likely from calibration-associated changes in gains. MPXI decreased with storage, and with variable changes between animals and analyzers. Platelet clumps and lipid contributed to the variability in replicate MPXI measurements.
MPXI has a higher variability in equine samples than in canine samples. Equivalent results might not be obtained between analyzers. Results change unpredictably with repeated analyses over 72 hours. MPXI measurements might only be useful in controlled research settings.
ADVIA 血液分析仪上的髓过氧化物酶指数 (MPXI) 反映了中性粒细胞髓过氧化物酶的平均染色。它被用作动物和人类炎症的标志物，但检测的可变性和储存稳定性尚不清楚。
我们旨在确定冷藏保存犬和马 EDTA 抗凝血液的 MPXI 精密度和稳定性，并比较两种分析仪之间的 MPXI 结果。
从三个基于人的对照品中测定了 20 或 21 天校准前后的批内变异系数 (CV)。在 1 天内对 14-16 只狗和 26 匹马的血液进行 4-10 次测定，以测量批内 CV。对 18 个犬样本和 35 个马样本的中位数对照品和单批结果进行了比较。对 10-12 只狗和 10-11 匹马的血液进行了采集后，24、48 和 72 小时冷藏保存的分析。
对照品的批间 CV 分别为 ADVIA 1 和 2 的 10.7%-15.9%和 6.4%-9.6%，校准前和 4.3%-7.7%和 2.8%-17.5%，校准后。犬和马样本的批内 CV 分别为 0.6%-64%和 3%-350%。分析仪之间的 MPXI 中位数结果差异显著，可能是由于增益相关的校准变化所致。MPXI 随储存而降低，并且在动物和分析仪之间变化不同。血小板聚集体和脂质导致重复 MPXI 测量的变异性。
MPXI 在马样本中的变异性高于犬样本。可能无法在分析仪之间获得等效结果。在 72 小时内重复分析时，结果会不可预测地变化。MPXI 测量结果可能仅在受控研究环境中有用。
