Use BISAP in adults with confirmed or strongly suspected acute pancreatitis within the first 24 hours of presentation or admission to support early risk stratification, triage (ward vs HDU/ICU) and timing of imaging or specialist review. It is not designed for chronic pancreatitis without an acute flare or for non-pancreatic abdominal pain.

Original evidence signal

Derived using Classification and Regression Tree (CART) analysis on 17,992 acute pancreatitis admissions from 212 US hospitals (2000–2001) and validated in a separate cohort of 18,256 admissions from 177 hospitals (2004–2005), using in-hospital mortality as the outcome.
BISAP assigns 1 point for each of five variables measured in the first 24 hours (BUN >25 mg/dL, impaired mental status, SIRS, age >60 years, pleural effusion) to give a total score from 0 to 5.
In the original validation cohort, BISAP discriminated mortality similarly to APACHE II (area under the ROC curve around 0.82 vs 0.83) while using far fewer variables.

Risk gradient

BISAP score	Approximate in-hospital mortality
0	~0.1–0.2%
1	~0.5–0.7%
2	~2%
3	~5–8%
4	~13–19%
5	>20%

Across multiple cohorts, mortality and severe complications increase stepwise with each additional point. Scores ≥3 consistently define a higher-risk group and are associated with increased odds of organ failure, persistent organ failure and pancreatic necrosis.

Guidelines and use

International guidance, including the 2019 World Society of Emergency Surgery (WSES) guideline for severe acute pancreatitis, recognises BISAP as a simple early risk-stratification tool and notes that scores ≥3 identify patients at higher risk who may benefit from closer monitoring or higher-level care.
BISAP performs best when calculated within the first 24 hours and used alongside clinical assessment, haemodynamic status, organ failure scores and imaging rather than as a stand-alone disposition rule.

Limitations

Evidence is drawn mainly from adult hospital cohorts. Data in children, pregnancy and some high-risk subgroups are limited.
BUN and SIRS criteria may be affected by pre-existing renal disease, sepsis or the timing and intensity of early resuscitation, so trends over time and overall clinical trajectory remain important.
BISAP predicts mortality and severe complications but does not replace local pancreatitis pathways for decisions about imaging, antibiotics, interventions or transfer.

BISAP Score for Pancreatitis Mortality