What lab tests are recommended for assessing pancreas and liver function?

Laboratory Tests for Pancreas and Liver Function Assessment

Liver Function Testing

For initial liver function assessment, order bilirubin, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT), together with a full blood count. 1, 2

Core Liver Panel Components

• Bilirubin (total) evaluates hepatic excretory function and detects cholestasis 2
• Albumin reflects hepatic protein synthesis capacity and represents true liver function 2
• ALT is the most specific marker for hepatocellular injury and should be the primary aminotransferase measured 1, 2
• ALP estimates impedance of bile flow and identifies cholestatic processes 1, 2
• GGT increases sensitivity for detecting liver disease and is associated with increased liver-related and all-cause mortality 1, 2
• Full blood count/platelet count is essential for detecting thrombocytopenia associated with portal hypertension and advanced liver disease 1, 2

Additional Liver Tests When Indicated

• AST (aspartate aminotransferase) should be added reflexively when ALT or GGT is abnormal to calculate the AST:ALT ratio, which provides critical information about fibrosis severity 2
• An AST:ALT ratio >1 indicates advanced fibrosis or cirrhosis, even when both values are within normal range 2
• Direct/conjugated bilirubin aids in interpreting elevated ALP and distinguishing cholestatic patterns 2

Critical Interpretation Principles for Liver Tests

• Normal ALT and AST can occur even with cirrhosis, making them unreliable for excluding advanced disease 2
• Use age and sex-normative values rather than generic upper limits of normal 2
• Transient elevations during systemic inflammation should not be confused with true liver disease; persistent abnormalities (>3-6 months) are more clinically significant 2

Pancreatic Function Testing

For suspected acute pancreatitis, order serum lipase as the single preferred test, with a diagnostic cutoff of ≥3 times the upper limit of normal. 1, 3, 4

Acute Pancreatitis Diagnosis

• Serum lipase is superior to amylase with higher sensitivity, longer diagnostic window (elevated 4-8 hours, peaks at 24 hours, normalizes over 8-14 days), and is the recommended first-line test 1, 3, 4
• Serum amylase can be used as an alternative but has less specificity and a shorter diagnostic window (rises 6-24 hours, peaks at 48 hours, normalizes over 3-7 days) 1, 3
• Co-ordering both lipase and amylase provides little to no increase in diagnostic sensitivity and represents unnecessary testing 4

Additional Labs for Acute Pancreatitis Severity and Etiology

When acute pancreatitis is confirmed, obtain these additional tests:

• Liver function tests (ALT, AST, ALP, bilirubin) to identify biliary etiology—peak ALT >150 U/L is highly diagnostic of biliary pancreatitis 1, 3, 5
• Serum triglycerides—levels >1000 mg/dL (11.3 mmol/L) indicate hypertriglyceridemia as the etiology 1, 3
• Serum calcium to identify hypercalcemia as a cause 1, 3
• C-reactive protein (CRP) at 48-72 hours—≥150 mg/L predicts severe disease 1, 3
• Hematocrit—>44% is an independent risk factor for pancreatic necrosis 1, 3
• Blood urea nitrogen (BUN)—>20 mg/dL predicts mortality 1, 3
• Procalcitonin is the most sensitive marker for detecting pancreatic infection, and low values strongly exclude infected necrosis 1, 3

Chronic Pancreatic Insufficiency Assessment

Do not use serum enzyme testing (lipase, amylase, trypsin) for diagnosing chronic pancreatitis or pancreatic insufficiency, as these lack sensitivity until disease is far advanced (>90% acinar tissue destruction required). 1, 3

• Fecal elastase is the recommended first-line test for chronic pancreatic insufficiency due to its convenience and acceptable reliability 3
• Fecal chymotrypsin alone is sufficient for patients with clearly normal or severely impaired function, but those with intermediate values require confirmatory testing 1, 3
• Serum enzyme levels remain normal in up to 50% of patients with marked functional impairment on invasive testing 1

Common Pitfalls to Avoid

• Do not rely on serum amylase or lipase levels to determine severity or etiology of acute pancreatitis—they cannot distinguish mild from severe disease 1, 6
• The lipase/amylase ratio does not reliably distinguish alcoholic from biliary pancreatitis and should not be used for this purpose 6, 5
• Serum amylase and lipase can be elevated in chronic liver disease (especially cirrhosis) due to decreased hepatic clearance, not pancreatic disease 7
• Measuring amylase within 3 hours of injury may miss up to 40% of pancreatic trauma cases; serial measurements every 6 hours improve accuracy 1