Autoimmune pancreatitis laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Iqra Qamar M.D.[2]

Laboratory findings consistent with the diagnosis of autoimmune pancreatitis may include increased serum IgG4 levels and hypergammaglobulinemia (>2 times the upper limit of normal in most patients), antilactoferrin antibody, anticarbonic anhydrase II antibody, other autoantibodies (ANA), rheumatoid factor (RF), IgG4-positive plasma cells, elevated serum alkaline phosphatase levels (ALP), elevated serum aminotransferases, ESR, and CA19-9.

Laboratory findings consistent with the diagnosis of autoimmune pancreatitis include:^{[1][2][3][4][5]}

• Increased serum IgG4 levels and hypergammaglobulinemia (>2 times the upper limit of normal in most patients). Using a cutoff of 135 mg/dL, serum IgG4 has following sensitivity and specificity:
  • Sensitivity 95%
  • Specificity 97%
• Antilactoferrin antibody
• Anticarbonic anhydrase II antibody
• Anti-plasminogen-binding protein (PBP) peptide antibodies^[6]
• Rheumatoid factor (RF)
• IgG4-positive plasma cells
• Elevated serum alkaline phosphatase levels (ALP)
• Elevated serum aminotransferases
• Elevated ESR
• Elevated CA19-9

• A non-specific, qualitative test that is no longer used for the diagnosis of steatorrhea.

• A quantitaive test that determines fecal fat excretion for over 24hrs.
• Fecal fat excretion of >7g/day is diagnostic of malabsorption.
• Patients with steatorrhea usually have an excretion of >10g of fat per day.

• The most sensitive and specific test for pancreatic exocrine dysfunction.
• It can be done with a single random stool sample.
• The results are independent of pancreatic enzyme replacement therapy.
• A value of less than 200 ug/g indicates pancreatic insufficiency.^{[7][8][9][10]}

• Direct tests are used to assess pancreatic insufficiency in the early course of disease when patient has clinical symptoms but no radiology findings.
• Direct tests involve pancreatic stimulation via meal or hormonal secretagogues and assessment of pancreatic secretions in the duodenal fluid.
• Direct tests along with radiographic findings (pancreatic calcifications) are stll considered to be the gold standard for the diagnosis of chronic pancreatitis.^{[11][12][13][14]}
• The limitation of direct tests is that they are costly and cumbersome.^{[11][12][13][14]}
• Direct tests include:
  • Secretin stimulation test
  • Pancreozymin-secretin test

Secretin stimulation test is considered the gold standard functional test for diagnosis of chronic pancreatitis.

The observation that bi-carbonate production is impaired early in chronic pancreatitis has led to the rationale of use of this test in early stages of disease:

• Sensitivity – 82%^[15]
• Specificity- 86%^[15]

Indirect tests are used to assess the complications of chronic pancreatitis.

• Indirect tests include:
  • Faecal chymotrypsin, PABA, pancreolauryl
  • Faecal elastase test

Indirect tests are not sensitive to assess pancreatic insufficiency in the early course of disease.^[14][16]

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