What laboratory tests are recommended for a patient with suspected pancreatitis, particularly one with a history of abdominal pain or dyspepsia?

Laboratory Tests for Suspected Pancreatitis

Serum lipase is the single preferred diagnostic test for acute pancreatitis, measured at admission with a diagnostic threshold of ≥3 times the upper limit of normal. 1, 2

Initial Diagnostic Testing

Primary Enzyme Test

• Measure serum lipase as the first-line test rather than amylase, as it demonstrates superior sensitivity (91% vs 62%) and specificity, particularly in alcoholic pancreatitis and when patients present days after symptom onset 1, 2, 3
• Lipase remains elevated longer in serum (8-14 days) compared to amylase (3-7 days), providing a wider diagnostic window 1, 4
• The diagnostic cutoff is ≥3 times the upper limit of normal for optimal balance between sensitivity and specificity 2, 3
• Do not co-order both amylase and lipase as simultaneous testing does not improve diagnostic accuracy and increases unnecessary costs 5, 4

Etiologic Workup at Admission

All patients require the following tests to identify the underlying cause 1, 2:

• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to evaluate for gallstone pancreatitis—the most common etiology 1, 2
• Serum triglycerides to identify hypertriglyceridemia; levels >1000 mg/dL definitively indicate this as the etiology 1, 2
• Serum calcium to assess for hypercalcemia as a potential cause 1

Severity Assessment Laboratory Markers

Timing-Specific Tests

• C-reactive protein (CRP) at 48 hours after symptom onset is the preferred laboratory marker for severity assessment; values >150 mg/L indicate severe disease 6, 1, 2, 5
• Procalcitonin (PCT) is the most sensitive laboratory test for detecting pancreatic infection, with low values strongly predicting absence of infected necrosis 6, 1

Prognostic Markers at Admission

• Hematocrit >44% represents an independent risk factor for pancreatic necrosis 1
• Blood urea nitrogen >20 mg/dL is an independent predictor of mortality 1
• White blood cell count should be monitored as part of inflammatory indices 6

Monitoring During Hospitalization

For Moderately Severe to Severe Cases

• Monitor hematocrit, blood urea nitrogen, and creatinine to assess fluid status and renal function 6
• Do not perform daily enzyme measurements after diagnosis is established, as they have no value in assessing clinical progress or prognosis 5

For Suspected Infected Necrosis

• PCT measurement is indicated when infection is suspected 6
• Consider CT- or EUS-guided fine-needle aspiration (FNA) for Gram stain and culture if infection remains unclear 6

Common Pitfalls to Avoid

• Do not rely on the degree of enzyme elevation to predict severity—patients can have severe pancreatitis with modest enzyme elevations 2
• Do not exclude pancreatitis based on normal amylase alone, particularly in hyperlipidemia-induced pancreatitis, acute-on-chronic pancreatitis, or delayed presentation 5
• Do not order extensive laboratory workup in patients <40 years with a single episode of unexplained pancreatitis—reserve invasive testing for recurrent episodes 1
• Clinical assessment alone is unreliable and will misclassify approximately 50% of patients, so objective laboratory criteria must support clinical judgment 6, 2