Tests and diagnosis

By Mayo Clinic Staff

Autoimmune pancreatitis is difficult to diagnose, because its signs and symptoms are very similar to those of pancreatic cancer. However, an accurate diagnosis is extremely important. Undiagnosed cancer may result in delaying or not receiving necessary surgery. On the other hand, having unneeded surgery that is invasive and risky also should be avoided.

There are two types of autoimmune pancreatitis. Doctors will use a number of tests to determine if you have AIP and if so, which type you have.

People with AIP type 1 have:

  • One or more masses in the pancreas.
  • A high level of (elevated) serum IgG4 in the pancreas.
  • In some cases, evidence of the disease in other organs, called other organ involvement (OOI), such as masses or elevated serum IgG4.
  • A rapid response to treatment with steroids.
  • A likelihood of relapse if treatment is discontinued.

In contrast, people with AIP type 2 have:

  • No evidence of the disease other than in the pancreas.
  • No serum IgG4 elevation.
  • No OOI.
  • GELs. Granulocyte epithelial lesions (GELS) are a type of white blood cell (neutrophils) in the ducts of the pancreas, often causing destruction of the ducts.
  • Little likelihood of relapse after treatment is discontinued.

Because people with AIP type 2 don't have elevated IgG4 or other organ involvement, a definitive diagnosis requires a biopsy (pancreatic histology).

Tests

No single test or characteristic feature identifies autoimmune pancreatitis. Until recently, different diagnostic approaches around the world made the diagnosis more difficult. Researchers established the International Consensus Diagnostic Criteria (ICDC) in 2011:

  • Microscopic analysis of cells and tissues (histology)
  • Imaging, such as CT, MRI or ERCP
  • Serology (serum IgG4 levels)
  • Other organ involvement
  • Optionally, response to steroid therapy — usually a two-week steroid trial

Specific tests may include:

  • Imaging tests. Tests of your pancreas and other organs may include CT, MRI, endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP).
  • Blood tests. You will be tested for elevated levels of an immunoglobulin called IgG4, produced by your immune system. People with type 1 AIP, but not with type 2 AIP, will have highly elevated blood levels of IgG4.

    However a positive test doesn't necessarily mean that you have the disease. A small number of people who don't have autoimmune pancreatitis, including some with pancreatic cancer, also have high blood levels of IgG4.

  • Endoscopic core biopsy. In this test, pathologists analyze a sample of pancreatic tissue in the laboratory. AIP has a distinctive appearance that is easily recognized under a microscope. Doctors insert a small tube (endoscope) through the mouth into the stomach and, guided by ultrasound, remove some tissue from the pancreas using a special needle.

    The challenge is obtaining a sample of tissue large enough to analyze, rather than just a few cells. This procedure is not widely available.

  • Steroid trial. Because autoimmune pancreatitis is the only pancreatic disorder known to respond to steroids, doctors sometimes use a trial course of this drug to confirm a diagnosis.
Dec. 20, 2014