Abstract: BACKGROUND: The ability to make outcome and mortality predictions is pivotal to clinical decision making in critically ill patients. Specific markers of inflammation and platelet activation derived from routine haematology profiles, such as neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR) and mean platelet volume (MPV), are widely accessible and low-cost parameters that have been previously utilised as prognostic tools in dogs with a variety of medical conditions. In humans, these parameters have also been applied in critically ill patients. HYPOTHESIS/OBJECTIVES: To investigate whether NLR, PLR and MPV can be used as prognostic biomarkers in a heterogeneous population of critically ill dogs. ANIMALS AND METHODS: The medical records of 200 dogs admitted to the ICU over a 3-year period were retrospectively reviewed. Binomial regression models were used to investigate associations between NLR, PLR and MPV and survival. In dogs that survived, Kaplan Meier plots, log-rank tests and cox proportional hazards models were used to investigate the association between NLR, PLR and MPV and length of hospitalisation. RESULTS: NLR values above normal were associated with longer hospitalisation and higher mortality. When excluding dogs with neoplasia, dogs with higher MPV or PLR values were more likely to die or be euthanised than those with lower values. CONCLUSIONS AND CLINICAL IMPORTANCE: The association of NLR on day of admission with length of hospitalisation and mortality suggests the potential for its use as a prognostic biomarker. Further studies are required to confirm whether this parameter can be used to help predict outcome in critically ill dogs.
