What tests should be ordered for a patient with suspected pancreas inflammation?

Diagnostic Testing for Suspected Pancreatic Inflammation

Order serum lipase as your primary and preferred diagnostic test for suspected acute pancreatitis. 1, 2

Initial Laboratory Testing

First-Line Test: Serum Lipase

• Lipase is the single best diagnostic test with superior sensitivity (79-89%) and specificity (89-94%) compared to amylase 2, 3
• Diagnostic threshold: ≥3 times the upper limit of normal is most consistent with acute pancreatitis 1, 2
• Lipase rises within 4-8 hours of pancreatic injury, peaks at 24 hours, and remains elevated for 8-14 days, providing a much larger diagnostic window than amylase 2, 3
• Lipase has particular advantage in alcohol-induced pancreatitis and when patients present days after symptom onset 3, 4

Why Not Amylase?

• Amylase has lower sensitivity (72%) and can be elevated in numerous non-pancreatic conditions including renal disease, appendicitis, cholecystitis, bowel obstruction, and head injuries 2, 5
• Amylase normalizes within 3-7 days, missing late presentations 2
• Ordering both lipase and amylase together provides no diagnostic advantage and wastes resources 5, 3

Additional Initial Laboratory Tests

At Admission, Also Order:

• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to evaluate for gallstone etiology and biliary obstruction 1
• Serum triglycerides - levels >1000 mg/dL (>11.3 mmol/L) indicate hypertriglyceridemia-induced pancreatitis 1, 2
• Serum calcium to identify hypercalcemia as a cause 1, 2
• Complete blood count for white blood cell elevation 1
• C-reactive protein (CRP) - though not for diagnosis, CRP ≥150 mg/L at 48 hours predicts severe disease 1

Imaging Studies

When to Order Imaging:

• Abdominal ultrasound at admission to look for gallstones or bile duct obstruction 1
• CT with IV contrast after 72 hours if predicted severe disease (clinical deterioration, organ failure) or APACHE II score >8 to assess for pancreatic necrosis 1
• Early CT (within 72 hours) may underestimate necrosis extent 1

Special Considerations

If Autoimmune Pancreatitis Suspected:

• Serum IgG4 level (>280 mg/dL is diagnostic for type 1 autoimmune pancreatitis) 6
• CA 19-9 may be elevated but is non-specific 6

Critical Pitfalls to Avoid:

• Do not use enzyme levels to predict severity - a patient with lipase 4x normal can have severe pancreatitis while another with 20x normal may have mild disease 2
• Do not repeat daily enzyme measurements - they have no value in monitoring clinical progress or prognosis once diagnosis is established 5
• Lipase <3x upper limit of normal has low specificity and is consistent with but not diagnostic of pancreatitis 1
• Normal amylase does not exclude pancreatitis in hyperlipidemia-induced cases, chronic pancreatitis exacerbations, or delayed presentations 5