What are the initial laboratory tests and management for pancreatitis?

Initial Laboratory Tests for Pancreatitis

At admission, obtain serum lipase (preferred over amylase), triglycerides, calcium, and liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to establish the diagnosis and identify the etiology of acute pancreatitis. 1

Diagnostic Enzyme Testing

Serum lipase is the preferred diagnostic test over amylase due to its superior sensitivity and specificity, particularly in alcoholic pancreatitis and when patients present days after symptom onset, as lipase remains elevated longer in serum. 2, 3 While amylase is widely available and technically simple, it has lower specificity and can miss cases of hyperlipidemic pancreatitis, acute-on-chronic pancreatitis, or delayed presentations. 4, 5

• Lipase achieves 100% sensitivity when measured within 0-1 days of symptom onset, compared to 95% for amylase, with optimal diagnostic accuracy at approximately twofold above the upper limit of normal. 6
• Simultaneous measurement of both amylase and lipase provides minimal additional diagnostic benefit and increases unnecessary laboratory costs without improving sensitivity or specificity meaningfully. 3, 6
• UK guidelines note that lipase is preferred for diagnosis when available (Grade A recommendation). 1

Etiologic Workup

All patients require a comprehensive etiologic evaluation at admission to identify the underlying cause, which should be established in at least 75% of cases. 1

Essential Initial Labs:

• Triglyceride levels to identify hypertriglyceridemia (levels >1000 mg/dL indicate this as the etiology). 1, 7
• Serum calcium to evaluate for hypercalcemia as a potential cause. 1, 7
• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) to assess for gallstone pancreatitis—the most common etiology in many populations. 1, 7

Important Caveat:

If triglyceride levels cannot be obtained at admission due to non-fasting status, measure fasting triglycerides after recovery when the patient has resumed normal intake. 1

Severity Assessment

C-reactive protein (CRP) measured at 48 hours after symptom onset is the preferred laboratory marker for severity assessment, with values >150 mg/L indicating severe disease. 1, 7, 4

Timing is Critical:

• Do not rely on CRP in the first 24-48 hours—it lacks predictive value early in the disease course. 1
• Clinical assessment in the first 24 hours, although specific, lacks sensitivity and must be supported by objective measures like APACHE II scoring (cutoff >8). 1

Additional Severity Markers:

• Hematocrit >44% represents an independent risk factor for pancreatic necrosis. 7
• Blood urea nitrogen >20 mg/dL is an independent predictor of mortality. 7
• Procalcitonin is the most sensitive test for detecting pancreatic infection, with low values strongly predicting absence of infected necrosis. 7

Imaging Studies

Abdominal ultrasonography should be obtained at admission to evaluate for cholelithiasis or choledocholithiasis, though pancreatic visualization is limited in 25-50% of cases. 1, 2

• Contrast-enhanced CT should be performed after 72 hours (not earlier) in patients with predicted severe disease (APACHE II >8) or evidence of organ failure, as early CT underestimates the extent of pancreatic necrosis. 1
• Endoscopic ultrasound (EUS) can be used as an accurate alternative to screen for gallstones and bile duct stones, either at admission or after recovery if initial ultrasound is inadequate. 1

Initial Management Priorities

All patients require vigorous fluid resuscitation, supplemental oxygen as needed, correction of electrolyte and metabolic abnormalities, and pain control. 1

Nutritional Support:

• Provide nutritional support in patients likely to remain NPO for more than 7 days, with nasojejunal tube feeding using elemental or semi-elemental formula preferred over total parenteral nutrition. 1

Gallstone Pancreatitis:

• Urgent ERCP (within 24 hours) is indicated for concomitant cholangitis. 1
• Early ERCP (within 72 hours) should be performed when there is high suspicion of persistent common bile duct stone (visible stone on imaging, persistently dilated CBD, or jaundice). 1

What NOT to Do

• Do not measure daily pancreatic enzymes after diagnosis is established—they have no value in assessing clinical progress or prognosis. 4
• Do not perform extensive evaluation in patients <40 years with a single episode of unexplained pancreatitis—reserve invasive testing for recurrent episodes. 1, 7
• Do not routinely administer antibiotics in mild pancreatitis—they are only warranted for specific infections (chest, urine, bile, or line-related). 1