What labs are recommended for diagnosing acute pancreatitis?

Laboratory Testing for Acute Pancreatitis

Serum lipase should be ordered as the single preferred diagnostic test for acute pancreatitis, with a diagnostic threshold of ≥3 times the upper limit of normal. 1

Primary Diagnostic Test

• Lipase is superior to amylase for diagnosing acute pancreatitis, with sensitivity of 79-89% and specificity of 89-94% 1
• Lipase has a larger diagnostic window, rising within 4-8 hours of pancreatic injury, peaking at 24 hours, and remaining elevated for 8-14 days (compared to amylase which normalizes sooner) 1
• Ordering both lipase and amylase together provides no diagnostic advantage and should be avoided 1
• The diagnostic threshold should be set at ≥3 times the upper limit of normal for optimal accuracy 1, 2

Essential Additional Laboratory Tests at Admission

All patients require the following labs to establish etiology and assess severity:

• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to evaluate for gallstone etiology and biliary obstruction 3, 1
• Serum triglycerides to identify hypertriglyceridemia-induced pancreatitis (levels >1000 mg/dL are diagnostic) 3, 1
• Serum calcium to identify hypercalcemia as a causative factor 3, 1
• Complete blood count for white blood cell elevation 1

Prognostic Laboratory Tests

For severity assessment after initial diagnosis:

• C-reactive protein (CRP) at 48 hours: CRP ≥150 mg/L predicts severe disease and complications 3, 1
• This timing is critical—CRP measured at 48 hours after disease onset is the preferred laboratory marker for predicting severity 3

Special Circumstances

• Serum IgG4 level should be ordered if autoimmune pancreatitis is suspected, with levels >280 mg/dL being diagnostic for type 1 autoimmune pancreatitis 1
• Fasting triglycerides should be measured after recovery if initial triglyceride levels could not be obtained at admission 3

Common Pitfalls to Avoid

• Do not use amylase as the primary test—it has inferior sensitivity, particularly in alcohol-induced pancreatitis 3, 4
• Do not order both lipase and amylase routinely, as this increases costs without improving diagnostic accuracy 4
• Neither lipase nor amylase is useful for monitoring disease progression or predicting severity once the diagnosis is established 5
• Do not rely on enzyme levels at the upper limit of normal—the diagnostic threshold must be 3-4 times the upper limit for adequate specificity 3