Myeloperoxidase deficiency in dogs observed with the ADVIA®120 A retrospective study

Objective: In contrast to humans, neutrophil myeloperoxidase deficiency (MPOD) has been rarely investigated in dogs. The hematology analyzer ADVIA(R)120 differentiates leukocytes based on the cellular volume and their myeloperoxidase concentration. The aim of this study was the characterization of myeloperoxidase deficiency in dogs and the evaluation of the diagnostic use of the ADVIA(R) 120 Myeloperoxidase Index (MPXI). Material and methods: ADVIA(R) peroxidase scatter plots indicative of MPOD were reviewed. Severity of MPOD was classified semiquantitatively in three groups (MPOD grade 1-3): MPOD grade 1 (MPOD-1): neutrophils showing an abnormal shift of the population, < 25% extending in the monocyte cluster and therefore mis-classified, MPOD-2: similar to 25-50% of neutrophils misclassified, MPOD-3: 50-100% of the neutrophils misclassified due to their location in the monocyte cluster. Sex, age, and breed of the dogs as well as diagnosis, and MPXI were recorded. Results: 29 dogs (nine females and 20 males belonging to 23 breeds) with 38 analyses consistent with M POD were found. Diseases were characterized by severe leukocyte consumption and included mainly parvovirosis (8/29), DIC/sepsis (3/29), pyometra, pyothorax, pneumonia, pancreatic abscess, and cystitis. A significantly lower mean MPXI in MPOD-3 was present in comparison to the mean MPXI of MPOD-1 (p < 0.05), however, there was a great overlap between the groups. Conclusion: Diseases associated with neutrophil consumption may show an acquired MPOD in dogs. High standard deviation limits the diagnostic use of the MPXI for detection of MPOD. Clinical relevance: The ADVIA(R) 120 cytograms are a good screening tool for detection of MPOD in dogs, but the use of the MPXI is impaired in this species.