Grey eosinophils in sighthounds : frequency in 3 breeds and comparison of eosinophil counts determined manually and with 2 hematology analyzers

BACKGROUND: Grey eosinophils (GE) reported to occur in Greyhounds, and occasionally in other breeds, have clear granules, probably due to abnormal staining properties. OBJECTIVES: The aims of this study were to investigate the frequency of GE in Greyhounds and 2 other sighthound breeds, and to assess the capacity of the ADVIA 120 and Sysmex XT-2000iV hematology analyzers to correctly identify GE. METHODS: Blood samples from 20 Greyhounds, 29 Italian Greyhounds, and 24 Whippets were analyzed using the ADVIA and Sysmex hematology analyzers, and blood smears stained with May-Grünwald Giemsa were evaluated microscopically. The frequency of samples with GE detected on smears was recorded for each breed. Manual and automated eosinophil counts were compared using a Wilcoxon signed-rank test. Agreement between methods was assessed using Passing-Bablok and Bland-Altman plots. RESULTS: GE were detected in all 3 breeds: 9/20 Greyhounds (45.0%), 10/29 Italian Greyhounds (34.5%), and 5/24 Whippets (62.5%) with no significant differences in the frequency of GE among the breeds. In samples containing GE, both analyzers underestimated the percentage of eosinophils and occasionally eosinophils were not detected at all. When a novel "GE gate" was used, the percentage of eosinophils reported by the Sysmex was similar to that obtained by manual counting. CONCLUSIONS: GE are found in the blood of sighthounds other than Greyhounds. Hematology analyzers may underestimate the percentage of GE, probably due to their abnormal physical or chemical features. Underestimation is slight and usually clinically insignificant, but occasionally eosinophils are completely misclassified. Using the Sysmex analyzer, a GE gate can be designed to normalize the eosinophil count.