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Use of a severity index should allow prediction of the small group of patients who are going to develop severe disease, characterized by organ system failure, pancreatic necrosis with or without infection, and increased mortality. Overall mortality for AP is 2% but this increases to 30% in those with severe disease [52,53]. However, Di et al. [53] found that the test characteristics and clinical utility of these AP severity scores remain uncertain. They did not find studies that directly assessed influence of these models on patient management.

Predicting severity of AP should be simple and allow prediction early in the patient’s course. This is best accomplished by the Bedside Index for Severity in Acute Pancreatitis (BISAP) or SIRS, which can predict severity within the first 24 hours. The BISAP includes blood urea nitrogen (BUN) greater than 25 mg/dl, impaired mental status (Glasgow Coma Scale score <15), SIRS score 2 or above, age over 60 years, and pleural effusion. One point is given for each and a score of more than 3 indicates an increased risk of death [54]. A follow‐up evaluation by Singh et al. [55] on the BISAP score reported that a score of 3 or more was associated with an increased risk of developing organ failure, persistent organ failure, and pancreatic necrosis.

SIRS is defined by the presence of two or more of heart rate above 90 bpm, respiratory rate above 20 breaths per minute or PaCO ₂ below 32 mmHg (4.3 kPa), body temperature below 36 or above 38°C, and leukocyte count less than 4 × 10⁹/l or more than 12 × 10⁹/l. Its presence during the first 24 hours of admission has high sensitivity for predicting severe disease (85%). However, persistent SIRS predicted the development of persistent organ failure in only a minority of patients [56].

On admission, hematocrit above 44% and rise in BUN at 24 hours may be optional predictive tools. Reducing BUN and hematocrit should be utilized to guide fluid resuscitation over the first 12–24 hours and are an accurate predictor of death [57]. We agree with Forsmark and Yadav [58] that monitoring serum BUN and hematocrit along with SIRS over the first 48 hours is simple and an effective scoring system for predicting severe AP.