Prognostic Accuracy of Serum Lactate and Quick Sequential Organ Failure Assessment for Predicting Mortality in Sepsis: A Prospective Observational Study

Introduction: Sepsis is a life-threatening condition associated with high mortality and organ dysfunction. Early identification of high-risk patients is essential for timely intervention. Aim: To analyse and compare the prognostic accuracy of serum lactate levels and quick Sequential Organ Failure Assessment (qSOFA) score for mortality in septic patients. Materials and Methods: A prospective observational study was conducted among 57 adult patients with suspected sepsis and qSOFA score ≥2 admitted to a tertiary care centre in Tamil Nadu, India, between March 2024 and October 2025. Clinical parameters, qSOFA score, serum lactate levels, vasopressor requirement, mechanical ventilation, and in-hospital mortality were recorded. Statistical analyses included Chi-square test, Mann-Whitney U test, logistic regression, and Receiver Operating Characteristic (ROC) curve analysis. Results: The overall in-hospital mortality rate was 31.6%. Nonsurvivors had significantly higher serum lactate levels compared to survivors (5.6 vs 2.8 mmol/L, p-value <0.001). Elevated serum lactate levels were significantly associated with increased vasopressor requirement, need for mechanical ventilation, and mortality. Serum lactate demonstrated superior prognostic performance compared to qSOFA, with a higher area under the ROC curve (AUC 0.841 vs 0.712, p-value=0.038). A lactate cut-off ≥3.9 mmol/L showed sensitivity of 83.3% and specificity of 79.5% for predicting mortality. Multivariate logistic regression identified serum lactate as an independent predictor of mortality. Conclusion: Serum lactate is a superior prognostic marker compared to qSOFA score for predicting mortality and severity of illness in sepsis patients. Early lactate assessment might improve risk stratification and clinical decision-making in resource-limited settings.