What lab workup is recommended for a patient suspected of having pancreatitis?

Laboratory Workup for Pancreatitis

Serum lipase is the preferred laboratory test for diagnosing acute pancreatitis, with a cutoff value of three times the upper limit of normal providing optimal diagnostic accuracy. 1

Initial Diagnostic Tests

• Serum lipase is the most reliable diagnostic marker with higher sensitivity and a longer diagnostic window (rises within 4-8 hours, peaks at 24 hours, remains elevated for 8-14 days) 2, 1
• Serum amylase can be used but has lower specificity and a shorter diagnostic window (rises within 6-24 hours, peaks at 48 hours, normalizes within 3-7 days) 2, 1
• Both tests should use a cutoff value of three times the upper limit of normal for optimal diagnostic accuracy 2, 1

Additional Laboratory Tests for Etiology Assessment

• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to evaluate for biliary etiology 2, 1
• Serum triglyceride levels (values >11.3 mmol/L or >1000 mg/dL indicate hypertriglyceridemia-induced pancreatitis) 2, 1
• Serum calcium to evaluate for hypercalcemia as a potential cause 2, 1
• Complete blood count with hematocrit (hematocrit >44% represents an independent risk factor for pancreatic necrosis) 2, 1

Severity Assessment Parameters

• C-reactive protein (CRP) ≥150 mg/L at 48-72 hours after onset is the best available laboratory marker for predicting severe acute pancreatitis 2, 1
• Blood urea nitrogen >20 mg/dL is an independent predictor of mortality 2, 1
• Hematocrit >44% indicates risk for pancreatic necrosis 2, 1
• Procalcitonin is the most sensitive laboratory test for detection of pancreatic infection 2, 1

Diagnostic Algorithm

1. Initial laboratory panel: 2, 1

   • Serum lipase (preferred) or amylase
   • Complete blood count with hematocrit
   • Comprehensive metabolic panel including BUN, calcium, and liver function tests
   • Triglyceride level

2. Diagnosis confirmation: 2, 1

   • If lipase or amylase >3× upper limit of normal, diagnosis of acute pancreatitis is confirmed
   • Proceed with etiology workup and severity assessment

3. Monitoring disease progression: 2, 1

   • Serial CRP measurements (peak at 48-72 hours)
   • Serial hematocrit and BUN measurements
   • Procalcitonin if infection is suspected

Important Clinical Considerations

• Lipase is more specific than amylase for pancreatic inflammation, but both can be elevated in non-pancreatic conditions 2, 3
• Simultaneous measurement of both amylase and lipase does not significantly improve diagnostic accuracy 3
• Normal amylase would usually exclude acute pancreatitis except in cases of hyperlipidemia, acute exacerbation of chronic pancreatitis, or delayed presentation 3
• Once diagnosis is established, daily enzyme measurements have no value in assessing clinical progress or prognosis 3
• Mild elevations of amylase and/or lipase (less than three times upper limit of normal) with nonspecific abdominal symptoms rarely indicate significant pancreatic pathology 4

Imaging Considerations

• Abdominal ultrasound should be obtained at admission to evaluate for gallstones 2
• Contrast-enhanced CT should be performed after 72 hours of illness in patients with predicted severe disease or evidence of organ failure 2