In-hospital Mortality in Patients with Lower Gastrointestinal Bleeding: Development and Validation of a Prediction Score

Background and study aims: Lower gastrointestinal bleeding (LGIB) is a common condition linked to increased morbidity, healthcare costs, and mortality. Currently, no prospectively validated prognostic model exists to predict mortality in LGIB patients. Our aim was to develop and validate a risk score that could accurately predict in-hospital mortality of patients admitted for LGIB. Patients and methods: Patient data from a nationwide cohort study in 15 centers in Italy (2019-2020) were used to derivate the risk score (Acute Lower gastrointestinal Bleeding and In-hospital mortality, ALIBI score); the model was then externally validated in a cohort of consecutive patients hospitalized for LGIB in 12 centers from six countries (Italy, Spain, France, Greece, Iran, Brazil) in 2020-2024. The main outcome was in-hospital mortality; we also reported rebleeding rates and in-hospital mortality rate stratified by risk score and timing of colonoscopy. Results: Among 1,198 patients in the derivation cohort, 105 (8.8%) rebled, 41 (3.4%) died. Age, Charlson Comorbidity Index (CCI), in-hospital onset, hemodynamic instability, and creatinine levels were independent predictors of in-hospital mortality. The model demonstrated excellent discrimination (AUROC=0.813, 95%-CI: 0.752-0.874) and calibration. In the validation cohort (n=752 patients), the model's good discrimination (AUROC=0.792, 95%-CI: 0.720-0.863) and calibration were confirmed. Patients were categorized as low (0-4 points, 1% mortality), intermediate (5-9 points, 4.6% mortality), or high risk (10-13 points, 19.1% mortality). Conclusions: A new validated score effectively predicts in-hospital mortality in LGIB patients, aiding in risk stratification and management.