# Association of the blood urea nitrogen to serum albumin ratio on prognosis in patients with bacterial meningitis: a retrospective cohort study

## TL;DR

A high blood urea nitrogen to albumin ratio at admission predicts worse outcomes in bacterial meningitis patients, offering a low-cost tool for early risk assessment.

## Contribution

This study establishes the BUN/ALB ratio as an independent predictor of poor prognosis in bacterial meningitis patients.

## Key findings

- Patients with higher BUN/ALB ratios had significantly worse neurological outcomes at 3 months.
- The highest BUN/ALB tertile showed a 20-fold increased risk of unfavorable outcomes after adjusting for confounders.
- The BUN/ALB ratio demonstrated strong discriminative ability with an area under the curve of 0.8.

## Abstract

Early identification of high-risk patients is crucial for improving outcomes of bacterial meningitis (BM) patients. The blood urea nitrogen to albumin (BUN/ALB) ratio has demonstrated prognostic value in various critical illnesses, but its role in BM remains unestablished.

This retrospective cohort study included 146 adult patients with microbiologically confirmed BM hospitalized between 2010 and 2025. BUN/ALB ratio within 6 hours of admission was calculated. Based on 3-month post-discharge modified Rankin Scale (mRS) scores, patients were dichotomized into favorable (mRS 0–2) and unfavorable (mRS 3–6) prognostic groups. Multivariable logistic regression was used to examine the association between BUN/ALB ratio and unfavorable outcome, adjusting for relevant confounders. The predictive performance was assessed using receiver operating characteristic curve analysis.

Among included patients, 87 (59.6%) had unfavorable outcomes. The unfavorable prognosis group exhibited significantly higher admission BUN/ALB ratios compared to the favorable group (5.23 vs. 2.86, P < 0.001). After adjustment for age, gender, diabetes history, headache, neurological deficits, pathogen type, and mechanical ventilation, patients in the highest BUN/ALB tertile (> 5.13) showed a 20-fold increased risk of unfavorable outcome compared to the lowest tertile (adjusted OR = 20.494, P < 0.001). A significant dose-response relationship was observed (P for trend <0.001). RCS analysis supported a linear association (P for no-linearity=0.1503). The BUN/ALB ratio demonstrated discriminative ability with an area under the curve of 0.8.

Admission BUN/ALB ratio independently predicts 3-month unfavorable neurological outcomes in BM patients. This routinely available, low-cost biomarker may serve as a practical tool for early risk stratification and could guide more intensive monitoring and intervention in high-risk patients.