What is the Bedside Index for Severity in Acute Pancreatitis (BISAP) score, how is it calculated, and how does it predict mortality and guide management?

BISAP Score in Acute Pancreatitis

What is BISAP?

The Bedside Index for Severity in Acute Pancreatitis (BISAP) is a 5-point prognostic tool that should be calculated within the first 24 hours of presentation to identify patients at increased risk of mortality and severe disease, with a score ≥2 serving as the critical cutoff for severe acute pancreatitis, organ failure risk, and need for ICU-level care. 1, 2

How to Calculate BISAP

The score assigns 1 point for each of the following five parameters present within 24 hours of admission: 2, 3

• Blood urea nitrogen >25 mg/dL
• Impaired mental status (Glasgow Coma Scale <15)
• Systemic inflammatory response syndrome (SIRS) present
• Age >60 years
• Pleural effusion detected on imaging

Total possible score ranges from 0 to 5 points. 2

Score Interpretation and Mortality Prediction

Critical Cutoff Values

• BISAP ≥2 is the statistically significant cutoff for severe acute pancreatitis, organ failure, and increased mortality risk. 1, 3 This threshold mandates immediate transfer to an intensive-care setting, ideally within 24 hours. 1

• BISAP ≥3 indicates significantly elevated mortality risk and ICU admission is strongly recommended. 3 At this threshold, the score demonstrates 100% sensitivity and 69.2% specificity for predicting mortality. 4

Predictive Performance

• The score achieves an area-under-the-curve (AUC) of approximately 0.80 for predicting severe pancreatitis and 0.93 for predicting organ failure. 1, 2 For mortality prediction specifically, the AUC ranges from 0.82 to 0.94 across validation studies. 5, 6

• BISAP identifies patients at heightened mortality risk BEFORE organ failure develops, unlike traditional 48-hour scoring systems. 1, 3 This represents its key clinical advantage over Ranson and Glasgow scores. 1

Comparison with Other Scoring Systems

Advantages Over Traditional Scores

• BISAP outperforms Ranson criteria, CT severity index, CRP, hematocrit, and BMI for predicting severity and organ failure. 3, 7 The diagnostic performance is comparable to APACHE-II (sensitivity approximately 70-74%, specificity approximately 86-90%) while being far simpler to compute at the bedside. 1

• BISAP can be completed within 24 hours, whereas Ranson and Glasgow scores require 48 hours, preventing early risk stratification and potentially delaying necessary interventions. 1, 3

Relative Performance

• BISAP demonstrates higher specificity (91%) but lower sensitivity (51-56%) compared to Ranson criteria and APACHE-II for both mortality and severe disease. 3, 8 This means BISAP will miss some high-risk patients but has fewer false positives. 3

• APACHE-II remains the gold-standard for ongoing daily monitoring despite its complexity, offering the highest predictive accuracy for mortality (AUC 0.88-0.93) among available scoring systems. 1, 2

Clinical Management Algorithm Guided by BISAP

Within First 24 Hours

• Calculate BISAP score immediately upon presentation. 1, 2
• Obtain baseline labs including CRP, hematocrit, and BUN. 1 Elevated hematocrit independently predicts pancreatic necrosis, and elevated BUN independently predicts mortality. 1
• Assess for clinical organ failure (pulmonary, circulatory, or renal), which constitutes severe disease regardless of scoring results and supersedes all scores. 1, 2

BISAP ≥2: Immediate Actions

• Transfer to ICU or step-down unit for intensive monitoring. 3 Most transfers occur within 72 hours, but ideally should happen within 24 hours. 1
• Do NOT initiate prophylactic antibiotics based on score alone (Grade 1A evidence). 1, 3 Prophylactic antibiotics provide no mortality or morbidity benefit in sterile necrosis and should be reserved only for documented infected necrosis. 1

48-Hour Reassessment

• If BISAP is high or clinical picture is equivocal, calculate APACHE-II score for ongoing monitoring. 1 An APACHE-II ≥8 defines severe acute pancreatitis; threshold ≥6 yields approximately 95% sensitivity for complications. 1, 2
• Repeat APACHE-II daily to track disease trajectory. 1

Day 3 Assessment

• Measure CRP on day 3; markedly elevated CRP (≥150 mg/L) indicates severe disease. 1, 2 Peak CRP >210 mg/L in the first four days predicts severity with approximately 80% accuracy. 1, 2

Days 3-10: Imaging

• Perform contrast-enhanced CT with CT Severity Index (CTSI) calculation in patients with predicted severe disease, but not before day 3 to avoid underestimation of necrosis. 1, 2 CTSI ≥3 indicates severe disease, with scores 7-10 associated with approximately 92% morbidity and 17% mortality. 1, 2

Critical Pitfalls to Avoid

• Do not rely on BISAP alone—combine with CRP trends and clinical organ-failure assessment for comprehensive risk stratification. 1, 3 Clinical assessment alone misclassifies roughly half of patients. 1

• Do not postpone aggressive management while awaiting 48-hour scores in patients with high BISAP or clear clinical severity. 1

• Recognize that BISAP has suboptimal sensitivity (51-56%), meaning it will miss some high-risk patients. 3, 8 Therefore, maintain high clinical suspicion even with lower scores if the patient appears clinically severe. 3

• Continuously monitor for development of organ failure, as its occurrence definitively defines severe disease and overrides all scoring systems. 1, 2

• Do not use procalcitonin for severity assessment—it is highly sensitive for detecting pancreatic infection, with low levels strongly predicting absence of infected necrosis, but should not guide initial severity grading. 1