Serum Anion Gap at Admission Predicts All-Cause Mortality in Critically Ill Patients With Cirrhosis: A Retrospective Cohort Study

INTRODUCTION: The primary objective of this study was to evaluate admission serum anion gap (AG) as a predictor of all-cause mortality in critically ill patients with cirrhosis. METHODS: A total of 3,084 cirrhotic patients were included and randomly divided into training and validation cohorts (n = 2,159 and 925, respectively). Patients were categorized into high and normal AG groups based on their AG values. Cox regression and Kaplan-Meier survival analysis were used to assess the relationships between AG levels and outcomes. RESULTS: Both cohorts showed strong parameter similarity (P > 0.05). High AG was associated with significantly lower survival probabilities. Cox models confirmed elevated AG as a risk factor, even after adjusting for covariates (hazard ratio: 1.920, 1.793, and 1.764 for 30-day, 60-day, and hospital mortality, respectively). Subgroup analyses, especially regarding chronic kidney disease, revealed complex interactions. Serum AG displayed predictive power comparable with established scoring systems. DISCUSSION: Elevated AG at admission is a valuable predictor of poor outcomes and increased mortality risk in critically ill cirrhotic patients. Serum AG can serve as an easily accessible tool for risk assessment and prognosis evaluation in this population.