Prognostic Efficacy of Complete Blood Count Indices for Assessing the Presence and the Progression of Myxomatous Mitral Valve Disease in Dogs

SIMPLE SUMMARY: The neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR) are inflammatory indicators calculated using blood counts that serve as potential biomarkers in various diseases. This study investigated healthy dogs and those with a common heart disease, myxomatous mitral valve disease (MMVD). Dogs with MMVD had higher NLR, MLR, and PLR, which could be useful for diagnosing and predicting this condition. ABSTRACT: This study investigated the complete blood count (CBC) indices, including neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR) in dogs with myxomatous mitral valve disease (MMVD) and analyzed their correlation with conventional biomarkers, as well as the effect of CBC indices on survival time in dogs with MMVD. Medical records of 75 healthy controls and 249 dogs with MMVD from March 2015 to October 2022 were analyzed. The NLR, MLR, and PLR were calculated by dividing the absolute counts of the CBC parameters. Dogs with MMVD had significantly higher NLR, MLR, and PLR than healthy dogs (all p < 0.0001), especially those in the symptomatic MMVD group with pulmonary edema (p < 0.0001, p = 0.0002, and p = 0.0387, respectively). The NLR and MLR were significantly correlated with N-terminal pro-B type natriuretic peptide levels (both p < 0.0001). The CBC indices showed potential as biomarkers for detecting the presence of MMVD (all p < 0.0001) and severity of MMVD (p < 0.0001, p < 0.0001, and p = 0.006, respectively) using receiver operating characteristic curve analysis. The negative effects of increased NLR, MLR, and PLR on survival were confirmed using Kaplan–Meier curve analysis. In conclusion, NLR, MLR, and PLR could be cost-effective and readily available potential diagnostic and prognostic biomarkers for MMVD in dogs.