In a female patient with acute pancreatitis (epigastric pain, nausea, vomiting, epigastric tenderness, elevated amylase), which laboratory marker best predicts disease severity: procalcitonin, aspartate aminotransferase (AST), C‑reactive protein (CRP), or erythrocyte sedimentation rate (ESR)?

C-Reactive Protein (CRP) Best Predicts Severity in Acute Pancreatitis

Among the listed options, C-reactive protein (CRP) is the preferred laboratory marker for predicting severity in acute pancreatitis, with guideline-recommended cutoffs of >150 mg/L at 48 hours or >120 mg/L at the end of the first week. 1

Guideline-Based Recommendations

CRP as the Standard Biomarker

• CRP >150 mg/L at 48 hours after disease onset is the guideline-preferred laboratory test for severity prediction, with an overall accuracy of approximately 80% 1
• The British Society of Gastroenterology recommends CRP assessment in all patients within 48 hours for severity stratification 1
• CRP maintains its predictive value when combined with clinical scoring systems like the Glasgow criteria, potentially improving prognostication 1

Why CRP Over Other Options

CRP demonstrates superior diagnostic performance compared to ESR and AST:

• Recent meta-analysis (2024) shows CRP has an AUC of 0.85 with sensitivity 76% and specificity 79% for predicting severe acute pancreatitis 2
• CRP at 36 hours with cutoff ≥150 mg/L provides sensitivity 86%, specificity 87%, and negative predictive value 93% 3
• CRP concentrations are superior to white cell count, ESR, and temperature for guiding clinical decisions 4

Procalcitonin: A More Specialized Role

While procalcitonin was not the guideline-preferred answer historically, newer evidence shows PCT has specific value for predicting infected pancreatic necrosis rather than initial severity assessment 5:

• The World Society of Emergency Surgery (Grade 1B) recommends PCT specifically for predicting risk of infected necrosis and guiding antibiotic decisions 5
• PCT demonstrates AUC of 0.929 for severe AP diagnosis with sensitivity 77.8% and specificity 94% 6
• PCT is most valuable as a negative predictor of infected necrosis, not for initial severity stratification 5

Why Not the Other Options

AST (Option B)

• AST is recommended at admission for etiological assessment (determining gallstone vs. other causes), not severity prediction 1
• Liver chemistries help identify biliary etiology but do not correlate with disease severity 1

ESR (Option D)

• ESR performs inferiorly to CRP with only 57% specificity at 36 hours (vs. 87% for CRP) 3
• ESR ≥60 mm/h at 36 hours has lower positive predictive value (48%) compared to CRP (75%) 3
• ESR is not mentioned in major guidelines as a severity predictor 1

Clinical Application Algorithm

For this patient with epigastric pain, vomiting, and elevated amylase:

1. Measure CRP at 48 hours post-admission as the guideline-recommended severity marker 1
2. If CRP >150 mg/L at 48 hours → predict severe disease and consider ICU triage 1
3. Combine CRP with APACHE II score (cutoff ≥8) for optimal severity assessment 1
4. Perform contrast-enhanced CT after 72 hours if CRP predicts severe disease to assess pancreatic necrosis 1
5. Reserve PCT measurement for monitoring infected necrosis risk if severe disease develops 5

Important Caveats

• CRP peaks at 36-48 hours, so early measurements (<24 hours) have limited predictive value 3, 4
• A persistently elevated CRP (>100 mg/L) at the end of the first week indicates enhanced risk of pancreatic collections 4
• Combined detection of multiple markers (CRP + PCT) can achieve AUC of 0.989, but CRP alone remains the guideline standard for initial assessment 6

Answer: C - CRP