What labs should be checked to diagnose pancreatitis?

Laboratory Tests for Diagnosing Pancreatitis

Serum lipase is the preferred laboratory test for diagnosing acute pancreatitis, with serum amylase, triglycerides, calcium, and liver chemistries (bilirubin, AST, ALT, alkaline phosphatase) recommended as part of the initial evaluation. 1, 2

Initial Laboratory Evaluation

First-line Tests

• Serum lipase: The most specific laboratory test (specificity 89-94%) and preferred over amylase 3

  • Remains elevated longer than amylase (larger diagnostic window)
  • Allows diagnosis in both early and late stages of acute pancreatitis
  • A cutoff of approximately 3-4 times the upper limit of normal improves diagnostic accuracy 4, 5

• Serum amylase: Still useful but has lower specificity than lipase 2

  • May be normal in certain conditions such as:
    • Hypertriglyceridemia-induced pancreatitis
    • Acute exacerbation of chronic pancreatitis
    • Delayed presentation (>3 days after symptom onset)

Additional Required Tests

According to the American Gastroenterological Association, the following tests should be obtained at admission 1:

• Triglyceride levels: To identify hypertriglyceridemia as a potential cause
• Calcium levels: To evaluate hypercalcemia as a potential cause
• Liver chemistries:
  • Bilirubin
  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
  • Alkaline phosphatase
  • Particularly helpful in identifying gallstone pancreatitis

Diagnostic Accuracy Considerations

• Lipase vs. Amylase: Multiple studies demonstrate that lipase offers higher sensitivity than amylase for diagnosing acute pancreatitis 2, 6
• Cutoff Values: Using cutoff values of 3-4 times the upper limit of normal significantly improves specificity for both enzymes 4
• Co-ordering: Simultaneous testing of both lipase and amylase provides minimal additional diagnostic benefit and increases costs unnecessarily 2, 6
• Timing: The diagnostic accuracy of both enzymes decreases with time from symptom onset, with lipase maintaining better sensitivity than amylase after 48 hours 6

Additional Laboratory Markers for Severity Assessment

• C-reactive protein (CRP): Preferred marker for severity assessment
  • A level >150 mg/L at 48 hours after disease onset indicates severe disease 1, 7
• Hematocrit and BUN: Should be monitored during the first 24 hours to assess fluid status and response to resuscitation 3

Common Pitfalls and Caveats

1. Mild elevations can be misleading: Mild elevations of amylase and/or lipase (<3 times upper limit of normal) may not indicate significant pancreatic pathology and extensive workup in these cases often has low diagnostic yield 5

2. Normal amylase doesn't exclude pancreatitis: In cases of hypertriglyceridemia-induced pancreatitis or delayed presentation, amylase may be normal despite active disease 7

3. Daily enzyme measurements not useful: Once diagnosis is established, repeated daily measurements of pancreatic enzymes do not help in assessing clinical progress or prognosis 7

4. Neither enzyme predicts severity or etiology: Laboratory tests alone cannot determine the severity or cause of pancreatitis; clinical assessment and imaging are required 7

5. Timing matters: The diagnostic value of both enzymes decreases significantly after 3-5 days from symptom onset 6

By following these evidence-based recommendations for laboratory testing, clinicians can accurately diagnose acute pancreatitis while avoiding unnecessary testing and costs.