nature publishing group ORIGINAL CONTRIBUTIONS PANCREAS AND BILIARY TRACT 1911 © 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY see related editorial on page x INTRODUCTION Acute pancreatitis (AP) is an inflammatory disease with a highly variable clinical course (1). This disease is currently the leading cause of gastrointestinal-related hospital admis- sions in the United States and continues to rise in incidence (2,3). Most patients (approximately 80%) with AP develop a mild course that results in a short, uncomplicated hospi- talization. The remaining 20% develop a complicated clini- cal course that requires prolonged hospitalization, intensive care, invasive interventions, and results in significant mortal- ity (3). he most widely accepted classiication system for severity in AP, the Atlanta classiication, was reported in 1992 (4). Atlanta 1992 divides AP into two groups: mild and severe. Severe disease is deined by the presence of organ failure (OF), local pancre- atic complications on imaging (acute luid collection, pancreatic necrosis (PNec), pseudocyst and pancreatic abscess), and/or poor prognostic scores (Ranson ’s ≥3 and/or APACHE-II ≥8) (4). Atlanta Revised Atlanta and Determinant-Based Classification: Application in a Prospective Cohort of Acute Pancreatitis Patients Haq Nawaz, MD 1 , Rawad Mounzer, MD 1 , Dhiraj Yadav, MD 1 , Jonathan G. Yabes, PhD 2 , Adam Slivka, MD, PhD 1 , David C. Whitcomb, MD, PhD 1 and Georgios I. Papachristou, MD 1,3 OBJECTIVES: Atlanta classification (Atlanta 1992) of acute pancreatitis (AP) has several limitations. Two new classification systems were recently proposed: the Atlanta reclassification (Atlanta 2012) and the determinant-based classification (DBC). The aim of our study was to: (i) determine the association between different severity categories and clinical outcomes and (ii) perform a head-to-head compari- son between Atlanta 1992, Atlanta 2012, and DBC in predicting these clinical outcomes. METHODS: A total of 256 prospectively enrolled patients were assigned a severity category for all three classi- fications. Five clinical outcomes were evaluated: mortality, intensive care unit (ICU) admission and length of stay (LOS), need for interventions, and hospital LOS. Pairwise testing between severity grades within a classification system was performed using Fisher’ s exact and Kruskal–Wallis tests. Predictive accuracies were evaluated using area under the ROC curve (AUC) and Somer’ s D co-efficient. RESULTS: Overall, higher grades of severity were associated with worse clinical outcomes for all three classifi- cation systems. Atlanta 2012 and DBC performed better than Atlanta 1992 and were comparable in predicting mortality (AUC 0.89 for both vs. 0.76, P < 0.001), ICU admission (AUC 0.91 for both vs. 0.80, P < 0.001), and ICU LOS (Somer’ s D 0.21 and 0.28 vs. 0.07, P < 0.05). DBC performed better in predicting need for interventions (AUC 0.93 vs. 0.85, P < 0.001), whereas Atlanta 2012 performed better in predicting hospital LOS (Somer’ s D 0.43 vs. 0.37, P = 0.04). CONCLUSIONS: Atlanta 2012 and DBC severity categories accurately reflected clinical outcomes in our cohort and were superior to Atlanta 1992. These novel classification systems can guide the selection of homoge- neous patient populations for clinical research and provide an accurate spectrum of disease severity categories in the clinical setting. Am J Gastroenterol 2013; 108:1911–1917; doi:10.1038/ajg.2013.348; published online 15 October 2013 1 Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University of Pittsburgh Medical Center , Pittsburgh, Pennsylvania, USA; 2 Center for Research on Health Care Data Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; 3 Division of Gastroenterology, Department of Medicine, Veterans Affairs Pittsburgh Health System, Pittsburgh, Pennsylvania, USA. Correspondence: Georgios I. Papachristou, MD, Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University of Pittsburgh Medical Center , Pittsburgh, Pennsylvania, USA. E-mail: papachri@pitt.edu Received 21 May 2013; accepted 19 August 2013