What labs are indicated for suspected pancreatitis?

Laboratory Tests for Suspected Pancreatitis

Serum lipase is the preferred initial laboratory test for suspected pancreatitis due to its superior sensitivity (100%) and specificity (99%) when elevated more than three times the upper limit of normal. 1

Essential Laboratory Tests

First-Line Tests

• Serum lipase: The primary diagnostic test with higher sensitivity (91%) than amylase, especially in alcohol-induced pancreatitis and in patients presenting later in the disease course 1, 2
• Liver function tests: Essential for identifying potential gallstone etiology 1
  • Aminotransferases (ALT, AST)
  • Bilirubin (total and direct)
  • Alkaline phosphatase
• Complete blood count: For assessing severity and complications
  • Elevated hematocrit >44% is an independent risk factor for pancreatic necrosis 1
• Blood urea nitrogen (BUN): Values >20 mg/dL independently predict mortality 1
• Glucose: Significant elevation indicates risk for severe disease 1

Second-Line Tests

• C-reactive protein (CRP): Order for prognostication in severe presentations
  • CRP ≥150 mg/L at 48-72 hours indicates severe disease with ~80% accuracy
  • Peak CRP >210 mg/L in first four days suggests severe disease 1
• Fasting lipid panel: To identify hypertriglyceridemia as a potential cause 1
• Calcium levels: To detect hypercalcemia as a possible etiology 1
• Serum amylase: Less sensitive (62%) than lipase but may be useful in specific scenarios 1, 2

Diagnostic Approach

1. Establish diagnosis: Requires at least two of three criteria:

   • Characteristic abdominal pain
   • Biochemical evidence (elevated serum lipase)
   • Characteristic imaging findings 1

2. Determine etiology:

   • Liver function tests for gallstone pancreatitis
   • Lipid panel for hypertriglyceridemia
   • Calcium levels for hypercalcemia 1

3. Assess severity:

   • BISAP score ≥2 indicates severe acute pancreatitis
   • APACHE-II score ≥8 indicates severe disease (95% sensitivity for complications)
   • CRP levels at 48-72 hours 1

Special Considerations

• Timing matters: Lipase remains elevated longer than amylase, making it more useful for patients presenting days after symptom onset 3
• False negatives: Normal amylase does not exclude pancreatitis in cases of hyperlipidemia, acute exacerbation of chronic pancreatitis, or delayed presentation 4
• Pregnancy: Include pregnancy test in women of childbearing age to rule out hyperemesis gravidarum or ectopic pregnancy 1
• Infection concerns: Order blood cultures and COVID-19 testing if infection is suspected 1

Common Pitfalls to Avoid

• Unnecessary dual testing: Simultaneous ordering of both lipase and amylase provides minimal additional diagnostic value and increases costs 1, 3
• Repeated enzyme measurements: Daily measurements of enzymes have no value in assessing clinical progress or prognosis once diagnosis is established 4
• Relying solely on enzyme levels: Remember that diagnosis requires clinical correlation (characteristic pain plus elevated enzymes or imaging findings) 1
• Missing biliary causes: Always check liver function tests, as elevated levels suggest gallstone pancreatitis requiring specific management 1
• Overlooking severity markers: Don't forget to assess BUN, hematocrit, and CRP for risk stratification 1

Follow-up Laboratory Testing

• Persistent symptoms with normal initial labs: Consider H. pylori testing, lipid panel, and other second-line tests based on clinical suspicion 1
• Monitoring during treatment: Follow BUN, hematocrit, and vital signs to assess response to fluid resuscitation 1
• Severe cases: Monitor CRP to assess disease progression 1