Neutrophil-to-lymphocyte ratio for primary risk stratification in acute pancreatitis: a systematic review and meta-analysis.

Background: Early risk stratification in acute pancreatitis should address not only the probability of severe disease but also the timely prediction of persistent organ failure, (POF) infectious complications [including infected pancreatic necrosis (IPN)], and mortality. The neutrophil-to-lymphocyte ratio (NLR) is a low-cost, first-line biomarker that is readily obtainable within the initial 24-48 h. Objective: To evaluate the clinical utility of the NLR for predicting a severe disease course, persistent organ failure, infection, and mortality across predefined, time-specific measurement windows. Methods: We conducted a systematic review with meta-analytic synthesis of studies assessing the NLR at admission and during the first two days of hospitalization. Random-effects models were used, and bivariate approaches were applied to synthesize diagnostic accuracy. Results: Elevated admission NLR was consistently associated with subsequent severe disease and an early need for intensive care. NLR dynamics on day 1 and day 2 preserved prognostic value and improved identification of patients at risk of persistent organ failure. NLR also helped identify individuals more likely to develop infectious complications, including infected pancreatic necrosis. An admission NLR > 12 was associated with in-hospital mortality. Overall, NLR showed acceptable discriminative performance with a favorable sensitivity-specificity profile and remained clinically useful for early triage. Conclusions: The NLR is a simple, reproducible tool for early prediction of organ failure, infection, and mortality in acute pancreatitis. The use of time-specific, locally calibrated thresholds, integrated with clinical scores and routine laboratory data, is recommended to optimize patient triage, routing, and care decisions. Systematic review registration: PROSPERO (CRD420251169592).