Comparative prognostic performance of quick sequential organ failure assessment, lactate, systemic inflammatory response syndrome criteria, and neutrophil-to-lymphocyte ratio for mortality prediction in critically ill dogs and cats

Background and Aim: Early identification of critically ill dogs and cats at high-risk of mortality is essential for timely intervention and improved clinical outcomes in veterinary emergency and critical-care practice. Several prognostic indicators, including the quick sequential organ failure assessment (qSOFA), blood lactate concentration, systemic inflammatory response syndrome (SIRS) criteria, and neutrophil-to-lymphocyte ratio (NLR), have been proposed for risk-stratification; however, comparative evidence in mixed populations of critically ill small animals remains limited. This study aimed to compare the prognostic performance of qSOFA, lactate, SIRS, and NLR for predicting mortality in critically ill dogs and cats admitted to a critical-care unit (CCU). Materials and Methods: A prospective cohort study was conducted on 76 client-owned critically ill animals, including 39 dogs and 37 cats, admitted to the CCU of the Small Animal Hospital, Chiang Mai University, Thailand. Admission qSOFA scores, blood lactate concentrations, SIRS criteria, and NLR values were recorded. Survival status at 21 days post-admission was used as the primary outcome measure. Prognostic performance was assessed using receiver operating characteristic curve analysis, area under the curve (AUC), sensitivity, and specificity at clinically relevant cut-offs. Results: The overall 21-day survival rate was 47.4%, with survival rates of 51.3% in dogs and 43.2% in cats. qSOFA demonstrated the best prognostic performance for mortality prediction, with an AUC of 0.72 (95% confidence interval CI: 0.61–0.82). Animals with qSOFA scores ≥ 2 showed significantly higher mortality risk. The combined qSOFA+lactate model produced a slightly higher AUC of 0.75 (95% CI: 0.62–0.88), although the improvement was not statistically significant. Lactate thresholds showed high sensitivity but poor specificity, particularly at lower cut-offs. SIRS and NLR exhibited limited discriminative ability and poor overall predictive performance. Among evaluated triage rules, qSOFA ≥ 2 provided the most balanced sensitivity and specificity for identifying non-survivors. Conclusion: qSOFA was the most reliable and clinically practical prognostic indicator among the evaluated parameters in critically ill dogs and cats. Lactate may serve as an adjunctive escalation marker for closer monitoring, whereas SIRS and NLR showed limited prognostic utility. These findings support the integration of qSOFA into evidence-based triage and risk-stratification protocols in veterinary critical-care. Keywords: cats, critical-care, dogs, lactate, mortality prediction, neutrophil-to-lymphocyte ratio, qSOFA, systemic inflammatory response syndrome.