Laboratory Assessment of Pancreatic Diseases

Acute Pancreatitis Labs - Enzyme Power Play

• Serum Amylase:
  • Rises: 2-12 hrs; Peaks: 24 hrs; Normalizes: 3-7 days
  • Diagnostic if >3x ULN (Upper Limit of Normal)
  • Less specific (e.g., mumps, renal failure)
• Serum Lipase:
  • Rises: 4-8 hrs; Peaks: 24 hrs; Normalizes: 8-14 days
  • Diagnostic if >3x ULN
  • More specific & sensitive; elevated longer.
  • 📌 Lipase: Lasts Longer, Leading diagnostic.
• Other Key Markers:
  • ↑ WBC (leukocytosis), ↑ Hct (initially, then ↓ if hemorrhage)
  • ↑ LDH, ↑ CRP (>150 mg/L at 48h suggests severity)
  • ↓ $Ca^{2+}$ (hypocalcemia - poor prognosis)
  • ↑ Glucose
  • ↑ BUN/Creatinine (renal function)

⭐ ALT >150 U/L strongly suggests gallstone pancreatitis.

Chronic Pancreatitis Tests - Function Under Fire

Evaluates exocrine pancreatic insufficiency (EPI).

• Direct Tests (Invasive, Gold Standard):
  • Secretin-CCK Test: Measures bicarbonate & enzyme output post-stimulation.
  • Endoscopic Pancreatic Function Test (ePFT): Endoscopic fluid collection.
• Indirect Tests (Non-invasive, Screening):
  • Fecal Elastase-1 (FE-1):
    • Normal: >200 µg/g stool.
    • Severe EPI: <100 µg/g.
  • Fecal Fat:
    • Sudan Stain (Qualitative).
    • 72-hr collection: >7 g/day abnormal (Steatorrhea gold standard).
  • Serum Trypsinogen: ↓ in severe EPI.
  • C13-Mixed Triglyceride Breath Test.

⭐ Fecal Elastase-1 is the most sensitive and specific indirect test for pancreatic exocrine insufficiency, unaffected by enzyme replacement therapy (PERT).

Pancreatic Cancer Markers - Tumour Trail Tidings

• CA 19-9 (Carbohydrate Antigen 19-9):
  • Primary serum marker for pancreatic ductal adenocarcinoma (PDAC).
  • Monitors therapy response, aids in detecting recurrence.
  • Not for screening (low specificity/prevalence).
  • Levels > 1000 U/mL suggest unresectability/metastasis.
• CEA (Carcinoembryonic Antigen):
  • Less sensitive/specific than CA 19-9 for PDAC.
  • Elevated in ~50% of cases; often used with CA 19-9.
  • Prognostic value; monitors recurrence.

⭐ CA 19-9 is absent in Lewis antigen (a-/b-) negative individuals (~5-10% population), leading to false negatives.

Pancreatic Cyst Fluid Analysis - Lesion Clues

• Amylase: High in pseudocysts; low in SCN, MCN, IPMN.
• CEA:

  • 192 ng/mL: Mucinous (MCN/IPMN).

  • < 5 ng/mL: SCN, pseudocyst.
• Glucose: < 50 mg/dL suggests malignancy.
• String Sign: Positive in mucinous cysts (viscous).
• Cytology: Malignant cells; low sensitivity.
• Molecular: KRAS (MCN, IPMN, PDAC), GNAS (IPMN).

⭐ CEA > 192 ng/mL strongly suggests a mucinous cyst (MCN/IPMN), guiding further management.

High‑Yield Points - ⚡ Biggest Takeaways

• Serum amylase & lipase are crucial for acute pancreatitis; lipase is more specific and elevated longer.
• Elevated amylase can be non-pancreatic (e.g., salivary disorders, renal failure).
• Fecal elastase-1 is the most sensitive test for exocrine pancreatic insufficiency.
• CA 19-9 is a tumor marker for pancreatic cancer, but not for screening.
• Genetic testing (PRSS1, SPINK1, CFTR) is vital for hereditary pancreatitis.
• Secretin stimulation test is gold standard for exocrine function but invasive.