Severity of myxomatous mitral valve disease in dogs may be predicted using neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratio.

Objective: To investigate the neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR) in dogs with myxomatous mitral valve disease (MMVD).
Animals: 106 dogs with MMVD and 22 healthy dogs were included in the study.
Procedures: CBC data were obtained retrospectively, and NLR, MLR, and PLR were compared between dogs with MMVD and healthy dogs. The ratios were also analyzed according to MMVD severity.
Results: NLR and MLR were significantly higher in dogs with MMVD C and D (NLR of 4.99 [3.69-7.27]; MLR of 0.56 [0.36-0.74]) than in healthy dogs (NLR: 3.05 [1.82-3.37], P < .001; MLR: 0.21 [0.14-0.32], P < .001), MMVD stage B1 (NLR: 3.15 [2.15-3.86], P < .001; MLR: 0.26 [0.20-0.36], P < .001), and MMVD stage B2 dogs (NLR: 3.22 [2.45-3.85], P < .001; MLR: 0.30 [0.19-0.37], P < .001). The area under the receiver operating characteristic curves of the NLR and MLR to distinguish dogs with MMVD C and D from those with MMVD B were 0.84 and 0.89, respectively. The optimal cutoff value for NLR was 4.296 (sensitivity, 68%; specificity, 83.95%), and the MLR value was 0.322 (sensitivity, 96%; specificity, 66.67%). NLR and MLR were significantly decreased after treatment in dogs with congestive heart failure (CHF).
Clinical Relevance: NLR and MLR can be used as adjunctive indicators of CHF in dogs.