Peer-reviewed veterinary case report
How stable is the myeloperoxidase index in dog and horse blood?
By Chu, Shelley Ann Ash & Stokol, Tracy·Published in Veterinary clinical pathology·2021·Department of Population Medicine and Diagnostic Science, United States·View original on PubMed →
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Original publication title: Assay variability and storage stability of the myeloperoxidase index of the ADVIA 2120i hematology analyzer in canine and equine whole blood samples.
Plain-English summary
This study looked at a blood test called the myeloperoxidase index (MPXI), which helps measure inflammation in dogs and horses. Researchers wanted to see how consistent and stable the test results were when using blood samples stored in the refrigerator. They found that the test results could vary quite a bit, especially in horses compared to dogs, and that results might not be the same between different machines. Additionally, the MPXI levels tended to drop when the blood samples were stored for longer periods, and factors like clumped platelets and fat in the blood could affect the results. Overall, the findings suggest that this test may not be reliable for routine use outside of controlled research environments.
Abstract
BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/33655602/