Laboratory Testing for Suspected Pancreatitis
Order serum lipase as the single primary diagnostic test for suspected acute pancreatitis, with a diagnostic threshold of ≥3 times the upper limit of normal. 1
Primary Diagnostic Test
- Lipase is superior to amylase with sensitivity of 79-89% and specificity of 89-94%, compared to amylase's lower sensitivity of 62-95% 1, 2
- Lipase rises within 4-8 hours of pancreatic injury, peaks at 24 hours, and remains elevated for 8-14 days—providing a larger diagnostic window than amylase 1
- Lipase is particularly superior in alcoholic pancreatitis and when patients present days after symptom onset 3, 4
- Do not order both lipase and amylase together—simultaneous testing provides no diagnostic advantage and wastes resources 1, 5
Essential Etiologic Workup at Admission
All patients require the following tests at admission to identify the underlying cause 6, 3:
- Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to evaluate for gallstone pancreatitis—the most common etiology 6, 1, 3
- Serum triglycerides to identify hypertriglyceridemia-induced pancreatitis (levels >1000 mg/dL are diagnostic) 6, 1, 7
- Serum calcium to assess for hypercalcemia as a potential cause 6, 1, 3
Critical Caveat for Triglycerides
- Measure triglycerides early at admission, as levels decrease rapidly with fasting and IV fluid administration 7
- If initial triglycerides are <1000 mg/dL but clinical suspicion remains high, repeat fasting triglycerides after recovery 7
Severity Assessment Laboratory Tests
- C-reactive protein (CRP) at 48 hours is the preferred laboratory marker for severity, with CRP ≥150 mg/L predicting severe disease 6, 1, 3
- Complete blood count for white blood cell elevation 1
- Hematocrit >44% is an independent risk factor for pancreatic necrosis 3
- Blood urea nitrogen >20 mg/dL independently predicts mortality 3
- Procalcitonin is the most sensitive test for detecting pancreatic infection, with low values strongly predicting absence of infected necrosis 3
Imaging Studies
- Abdominal ultrasound at admission to evaluate for gallstones or bile duct obstruction 6, 1, 3
- Contrast-enhanced CT after 72 hours (not earlier) in patients with predicted severe disease (APACHE II score >8) or evidence of organ failure—early CT underestimates pancreatic necrosis 6, 1, 3