Retrospective Evaluation of Hematological Ratios in Dogs With Nonassociative Immune-Mediated Hemolytic Anemia: 206 Cases

BACKGROUND: The utility of hematological ratios in immune-mediated hemolytic anemia (IMHA) in dogs has seldom been investigated. HYPOTHESIS: Hematological ratios are associated with disease severity and outcome in dogs with IMHA. ANIMALS: Two hundred and six client-owned dogs with non-associative IMHA. METHODS: Retrospective multicenter study. Medical records were reviewed to identify dogs with non-associative IMHA. The neutrophil-to-lymphocyte (NLR), neutrophil-to-monocyte (NMR), band neutrophil-to-segmented neutrophil (BNR), platelet-to-lymphocyte (PLR), monocyte-to-lymphocyte (MLR), neutrophil-to-platelet (NPR) and red blood cell distribution width-to-platelet (RDWPR) ratios were retrospectively calculated. Their association with hematological variables, number of blood transfusions, and survival at discharge, 1 month, and 6 months was evaluated. RESULTS: Of the 206 dogs included, 164 (80%, 95% confidence interval [CI]: 74-85), 144 (70%, 95% CI: 64-76), and 114 (55%; 95% CI: 48-62) were alive at discharge, one month, and six months, respectively. The hematological ratios were not associated with survival at any time point, regardless of treatment before referral. Only the RDWPR was associated with blood product requirement (odds ratio [OR], 0.70; 95% CI: 0.54-0.91; p < 0.01). Dogs that had received glucocorticoids before referral had a higher 1-month mortality rate compared with glucocorticoid-naïve dogs (73% and 67%, respectively; OR, 2.2; 95% CI: 1.1-4.5; p = 0.03). CONCLUSIONS AND CLINICAL IMPORTANCE: Hematological ratios had limited value in predicting outcome or disease severity in a large population of dogs with non-associative IMHA. Glucocorticoid treatment before referral was independently associated with decreased survival, likely reflecting selection bias toward dogs with more severe disease.