AIM:To investigate the prognostic usefulness of several existing scoring systems in predicting the severity of acute pancreatitis(AP).METHODS:We retrospectively analyzed the prospectively collected clinical database from consecutive patients with AP in our institution between January 2011 and December 2012.Ranson,Acute Physiology and Chronic Health Evaluation(APACHE)-Ⅱ,and bedside index for severity in acute pancreatitis(BISAP)scores,and computed tomography severity index(CTSI)of all patients were calculated.Serum C-reactive protein(CRP)levels were measured at admission(CRPi)and after 24h(CRP24).Severe AP was defined as persistent organ failure for more than 48 h.The predictive accuracy of each scoring system was measured by the area under the receiver-operating curve(AUC).RESULTS:Of 161 patients,21(13%)were classified as severe AP,and 3(1.9%)died.Statistically significant cutoff values for prediction of severe AP were Ranson≥3,BISAP≥2,APACHE-Ⅱ≥8,CTSI≥3,and CRP24≥21.4.AUCs for Ranson,BISAP,APACHE-Ⅱ,CTSI,and CRP24 in predicting severe AP were 0.69(95%CI:0.62-0.76),0.74(95%CI:0.66-0.80),0.78(95%CI:0.70-0.84),0.69(95%CI:0.61-0.76),and0.68(95%CI:0.57-0.78),respectively.APACHE-Ⅱdemonstrated the highest accuracy for prediction of severe AP,however,no statistically significant pairwise differences were observed between APACHE-Ⅱand the other scoring systems,including CRP24.CONCLUSION:Various scoring systems showed similar predictive accuracy for severity of AP.Unique models are needed in order to achieve further improvement of prognostic accuracy.