What labs should be ordered for suspected pancreatitis?

Laboratory Tests for Suspected Pancreatitis

For suspected pancreatitis, serum lipase and amylase should be obtained, along with triglyceride level, calcium level, and liver chemistries (bilirubin, AST, ALT, and alkaline phosphatase) at admission. 1

Initial Laboratory Evaluation

First-line Laboratory Tests

• Serum lipase: Preferred over amylase due to higher sensitivity and longer elevation window (remains elevated longer than amylase) 2
• Serum amylase: Alternative diagnostic marker, but less specific than lipase 3
• Liver chemistries:
  • Bilirubin
  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
  • Alkaline phosphatase
• Triglyceride level: Important to identify hypertriglyceridemia as potential etiology
• Calcium level: To evaluate for hypercalcemia as potential cause

Additional Laboratory Tests

• Complete blood count: To assess for leukocytosis
• C-reactive protein (CRP): Useful for severity assessment; levels >150 mg/L at 48 hours after disease onset indicate severe disease 1
• Procalcitonin (PCT): Most sensitive test for detection of pancreatic infection 1
• Blood urea nitrogen (BUN): For monitoring fluid status and renal function
• Creatinine: For assessing renal function

Diagnostic Accuracy Considerations

Serum lipase offers several advantages over amylase:

• Higher sensitivity for diagnosing acute pancreatitis 2
• Longer diagnostic window (remains elevated longer) 2
• Better sensitivity in alcoholic pancreatitis and delayed presentations 3

However, it's important to note that:

• Neither test is 100% specific for pancreatitis 3
• Simultaneous testing of both amylase and lipase does not significantly improve diagnostic accuracy and increases costs unnecessarily 2
• In rare cases, acute pancreatitis can present with normal lipase levels 4

Imaging Studies

After laboratory tests, imaging studies should be considered:

• Abdominal ultrasonography: Should be obtained at admission to look for cholelithiasis or choledocholithiasis 1
• CT with IV contrast: Should be performed selectively after 72 hours of illness in patients with:
  • Predicted severe disease (APACHE II score >8)
  • Evidence of organ failure during initial 72 hours 1
• MRI: Preferable in patients with contrast allergy or renal impairment 5
• Endoscopic ultrasonography (EUS): Can be used as an alternative to screen for cholelithiasis and choledocholithiasis 1

Common Pitfalls to Avoid

1. Relying solely on amylase: Lipase is more sensitive and specific, particularly in alcoholic pancreatitis and delayed presentations
2. Ordering both lipase and amylase routinely: This increases costs without significantly improving diagnostic accuracy 2
3. Performing early CT scans: CT should be performed selectively after 72 hours of illness onset to assess pancreatic necrosis in severe cases 1
4. Missing non-biliary causes: Always check triglycerides and calcium levels to identify other potential etiologies 1
5. Failing to repeat ultrasound: If initial ultrasound is inadequate or suspicion of gallstone pancreatitis remains high, repeat ultrasonography after recovery 1

By following this systematic approach to laboratory testing for suspected pancreatitis, clinicians can efficiently diagnose the condition, assess its severity, and identify potential causes, leading to appropriate management and improved patient outcomes.