Utility and prognostic significance of leukocyte ratios in dogs with Primary Immune‑Mediated Hemolytic Anemia

Canine immune-mediated hemolytic anemia (IMHA) is a life-threatening condition that is commonly associated with neutrophilia and monocytosis. Leukocyte ratios have been found to have prognostic value in humans and animals affected by a range of inflammatory, infectious, and neoplastic disorders. We hypothesized that in primary IMHA, neutrophil to lymphocyte (NLR), neutrophil to monocyte (NMR), band neutrophil to segmented neutrophil (BNR) and monocyte to lymphocyte (MLR) ratios would be higher in dogs that did not survive to discharge. Medical records of dogs diagnosed with IMHA at two veterinary teaching hospitals were retrospectively reviewed. Twenty-three of the 72 included dogs did not survive to discharge. NLR, NMR, BNR and MLR ratios were compared between dogs that survived to discharge and dogs that died or were euthanized. None of the ratios were significantly different between survivors and non-survivors (P = 0.14–0.99). Area under the Receiver Operating Characteristic (ROC) curve for prediction of non-survival ranged from 0.5 (95% confidence interval 0.38–0.62) for MLR to 0.61 (0.49–0.72) for NMR and was not significantly different from 0.5 for any ratio (P = 0.29–0.99). After exclusion of 31 dogs that received one or both immunosuppressive medications and blood transfusion before presentation, the area under the ROC curve for prediction of survival was significantly different from 0.5 for MLR (0.78, P = 0.01) and NMR (0.78, P = 0.0002). This study suggests that lower MLR and higher NMR may predict poorer prognosis in untreated dogs with IMHA.