BISAP Score in Acute Pancreatitis Assessment
The BISAP score is a simplified 5-point bedside tool that should be calculated within the first 24 hours of presentation to identify patients at increased risk of severe acute pancreatitis, organ failure, and mortality, with a score ≥2 serving as the critical cutoff for severe disease requiring ICU-level monitoring. 1, 2
What BISAP Measures
The BISAP score evaluates five parameters within 24 hours of admission 2:
- Blood urea nitrogen >25 mg/dL
- Impaired mental status
- Systemic inflammatory response syndrome (SIRS)
- Age >60 years
- Pleural effusion on radiography
Each parameter scores 1 point, for a maximum score of 5 2.
Critical Score Thresholds and Clinical Actions
BISAP ≥2: This is the statistically significant cutoff for severe acute pancreatitis and organ failure 1, 3. Patients meeting this threshold should be considered for ICU-level monitoring or step-down unit admission 1.
BISAP ≥3: This indicates significantly elevated mortality risk, and ICU admission is strongly recommended 1. In validation studies, a BISAP ≥3 demonstrated 79.79% sensitivity and 91.57% specificity for identifying severe acute pancreatitis, with a negative predictive value of 94.99% 4.
Performance Characteristics
The BISAP score demonstrates strong predictive accuracy 5, 3:
- Area under the curve (AUC) of 0.80 for predicting severe pancreatitis 2
- AUC of 0.93 for predicting organ failure 2
- AUC of 0.86 for predicting mortality 3
The key advantage is that BISAP identifies patients at increased risk of mortality before the onset of organ failure, unlike traditional scoring systems 1.
Comparative Advantages Over Other Scoring Systems
Timing advantage: BISAP can be calculated within the first 24 hours of admission, while Ranson criteria and APACHE-II require 48 hours for full assessment 1, 2.
Superior predictive performance: BISAP outperforms Ranson criteria, CT severity index, CRP, hematocrit, and BMI for predicting severity and organ failure 1, 3.
Simplicity: The BISAP score is similar in accuracy to the APACHE-II score (AUC 0.80 vs 0.80 for severe pancreatitis) but is much simpler to calculate at the bedside 2, 5.
Important Clinical Limitations and Caveats
Suboptimal sensitivity: BISAP has only 51-56% sensitivity for both mortality and severe disease, meaning it will miss some high-risk patients 1. This is a critical limitation that requires complementary assessment strategies.
Should not be used in isolation: BISAP score should be complemented with clinical judgment, CRP at 48-72 hours, and CT severity index 1. The American College of Surgeons recommends using BISAP as the primary scoring system due to its simplicity and accuracy, but recognizes the need for comprehensive assessment 2.
Variable positive predictive value: The positive predictive value of BISAP varies by population and disease prevalence 1.
Recommended Clinical Algorithm
Within first 24 hours:
- Calculate BISAP score immediately upon presentation 2
- Measure baseline CRP 2
- Monitor continuously for organ failure development 2
- Transfer patients with BISAP ≥2 to ICU-level monitoring or step-down unit 1
- Transfer patients with BISAP ≥3 to ICU 1
At 48 hours:
- Consider calculating Ranson or Glasgow score if BISAP is equivocal 2
- Use APACHE-II for ongoing daily monitoring in severe cases 2, 6
Days 3-10:
- Perform contrast-enhanced CT with CT Severity Index calculation in all patients with predicted severe disease 2, 6
- Measure CRP on day 3 (≥150 mg/L indicates severe disease with 80% accuracy) 2, 6
Common Pitfalls to Avoid
Do not administer prophylactic antibiotics based on high BISAP score alone - antibiotics should only be given for documented infected necrosis 1, 6.
Do not perform CT scans too early - imaging before day 3 may underestimate the extent of necrosis 6.
Do not rely on BISAP alone - the suboptimal sensitivity means some high-risk patients will be missed without complementary assessment 1.