Development and internal validation of the SCAN score: a pragmatic bedside tool for early prediction of spontaneous bacterial peritonitis in patients with cirrhosis and ascites

Introduction
Delays in diagnostic paracentesis for suspected spontaneous bacterial peritonitis (SBP) contribute to preventable mortality in cirrhosis. This study aimed to develop and internally validate a pragmatic bedside score using routinely available admission variables to stratify the risk of SBP at hospital presentation.

Material and methods
In this retrospective single-center cohort study, 1,312 consecutive adults with cirrhosis and ascites admitted between January 2020 and January 2025 were screened. A total of 1,000 unique patients met the eligibility criteria and were randomly divided into derivation (n = 700) and validation (n = 300) cohorts. SBP was defined as an ascitic polymorphonuclear leukocyte count ≥ 250/mm3. Multivariable logistic regression was used to identify independent predictors, which were incorporated into a four-component bedside score (SCAN: serum sodium, C-reactive protein, age, and neutrophil-to-lymphocyte ratio). Model discrimination and calibration were assessed.

Results
Spontaneous bacterial peritonitis was diagnosed in 185 patients (18.5%). In the validation cohort, the SCAN score demonstrated good discriminatory performance (AUROC 0.91, 95% CI: 0.87-0.94) and acceptable calibration (slope 0.96, Brier score 0.06). The probability of SBP increased progressively from 2.2% at a score of 0 to 75.0% at scores of 5-6. A prespecified cut-off of ≥ 3 points yielded a sensitivity of 88.1% and a specificity of 91.7%.

Conclusions
The SCAN score is a simple bedside tool that stratifies the risk of spontaneous bacterial peritonitis using routine admission variables. It may assist clinicians in prioritizing timely diagnostic evaluation, complementing guideline-recommended management. Prospective multicenter validation studies are warranted.