Prognostic value of the blood urea nitrogen-to-albumin ratio for 28-day mortality in septic intensive care unit patients: a large-scale retrospective cohort study using the Medical Information Mart for Intensive Care IV database

SUMMARY

Objective

Sepsis is a life-threatening condition characterized by dysregulated host responses to infection and high mortality in intensive care units. Existing prognostic models are often complex or resource-intensive. The blood urea nitrogen-to-albumin ratio, reflecting renal function, metabolic stress, and nutritional status, has emerged as a potential prognostic biomarker. The aim of this study was to evaluate the predictive value of blood urea nitrogen-to-albumin ratio for 28-day mortality in septic intensive care unit patients.

Methods

This retrospective cohort study utilized data from the Medical Information Mart for Intensive Care IV (version 2.0) database. Adult patients meeting Sepsis-3 criteria were included. Suspected infection was defined by antibiotic administration and microbiological culture within 24 h. Demographic, clinical, and laboratory data were collected, and blood urea nitrogen-to-albumin ratio was calculated using values obtained within the first 24 h of intensive care unit admission. Receiver operating characteristic curve analysis, Kaplan-Meier survival analysis, and multivariate Cox regression were performed.

Results

A total of 6,940 patients were included, with a 28-day mortality rate of 21.6%. Blood urea nitrogen-to-albumin ratio demonstrated superior predictive performance (area under the curve (AUC)=0.647, 95%CI 0.631–0.664) compared with serum urea (AUC=0.634) and albumin (AUC=0.428), and also outperformed the Sequential Organ Failure Assessment score (AUC=0.613). The optimal cutoff value was 7.6. Patients with blood urea nitrogen-to-albumin ratio ≥7.6 had significantly higher mortality than those with lower values (p<0.001). Elevated blood urea nitrogen-to-albumin ratio remained an independent predictor of mortality after adjustment.

Conclusion

Blood urea nitrogen-to-albumin ratio is a simple, objective, and readily available biomarker associated with 28-day mortality in septic intensive care unit patients and may contribute to risk stratification when used alongside other clinical parameters.