Hematologic Abnormalities and Diseases Associated with Moderate-to-Marked Basophilia in a Large Cohort of Dogs.

Basophilia is a rare hematologic finding in dogs. This research aimed to describe the hematologic and clinical characteristics of dogs with moderate-to-marked basophilia. CBC reports with blood smear examinations from dogs presented to the North Carolina State University Veterinary Teaching Hospital were retrospectively reviewed for basophilia (>193 cells/µL). We classified basophilia as moderate when counts were ≥500 cells/µL and marked when they reached ≥1000 cells/µL. We compared the hematologic and clinical profiles of dogs with moderate-to-marked basophilia (the basophilia group) to those without basophilia, serving as our control group. In addition, we investigated differences between dogs with marked basophilia versus those with moderate basophilia, as well as between dogs in the basophilia group with and without concurrent eosinophilia. Diseases associated with moderate-to-marked basophilia included eosinophilic lung disease ( p < 0.0001), leukemia/myeloproliferative neoplasms ( p = 0.004), parasitic infection ( p = 0.004), mast cell tumor ( p = 0.005), and inflammatory bowel disease ( p = 0.02). Overall, dogs with marked basophilia had a lower frequency of inflammatory diseases (51% vs. 70%, p = 0.009) and a higher frequency of neoplastic diseases (48% vs. 26%, p = 0.003) compared to those with moderate basophilia. In the basophilia group, concurrent eosinophilia was only seen in 36% of dogs. Dogs with concurrent eosinophilia were more often diagnosed with inflammatory diseases (77% vs. 58%, p = 0.006), with fewer diagnoses of neoplasia (19% vs. 40%, p = 0.001), compared to dogs without concurrent eosinophilia. The findings of this study offer veterinary clinicians valuable guidance in determining diagnostic priorities for dogs with moderate-to-marked basophilia.