Aim: Coagulation disorders may develop in association with severe acute pancreatitis (AP). Plasma thrombin- antithrombin III complex (TAT) levels are one of the principal markers of coagulation disorder. The purpose of this study was to evaluate TAT and other hemostatic parameters in patients with AP and to examine whether or not these parameters indicate the severity of AP. Method: Forty-six patients with AP (14 severe, 32 non-severe) and a 30-member healthy control group were recruited. The severity of AP was determined using the revised Atlanta classification. ELISA was used to measure patients' plasma TAT levels. Results: The TAT levels of AP patients at presentation were higher than those of the control group (p = 0.005). The plasma TAT levels of patients with severe AP were also significantly higher than those of patients with non-severe AP (p = 0.05) and of the control group (p < 0.001). The general accuracy, sensitivity and specificity of TAT levels in predicting the severity of AP were 77.4, 77.8, and 77.3% respectively. Conclusion: The coagulation cascade was activated in the AP patients in our study, and this was shown to become more pronounced as severity of the disease increased. Plasma TAT levels at the time of presentation in patients with AP can be used as a marker for predicting the severity of the disease. (c) 2018 S. Karger AG, Basel.