Patient Test Information

ANCA_MPO_PR3 Antibodies

Also known as:

ANCA Antibodies; cANCA; pANCA; Serine Protease 3; MPO; PR3; Anticytoplasmic Autoantibodies; 3-ANCA; PR3-ANCA; MPO-ANCA

Formal name:

Antineutrophil Cytoplasmic Antibodies; Myeloperoxidase Antibodies; Proteinase 3 Antibodies

Related tests:

Autoantibodies; Complete Blood Count; ESR; C-Reactive Protein; Complement; Urinalysis; ASCA; Calprotectin; Lactoferrin

Why Get Tested?

To help detect, aid in the diagnosis of, and sometimes monitor certain forms of the autoimmune disorder systemic vasculitis (inflammation of blood vessels)

To help distinguish between Crohn disease (CD) and ulcerative colitis (UC), the two most common types of inflammatory bowel disease (IBD); as an adjunct to other IBD testing

When to Get Tested?

When you have symptoms such as fever, muscle aches, and weight loss that your health practitioner thinks may be due to a vascular autoimmune disorder; sometimes to monitor response to therapy

When you have symptoms such as persistent or intermittent diarrhea and abdominal pain that your health practitioner suspects may be due to an IBD; when your health practitioner wants to distinguish between CD and UC

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

How is it used?

Tests for antineutrophil cytoplasmic antibodies (ANCA) may be used to:

  • Help detect and diagnose certain forms of autoimmune vasculitis, including granulomatosis with polyangiitis (Wegener granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome). Sometimes this test may also be used to monitor treatment and/or detect a relapse of these conditions. (For more detailed information on these conditions, see the article on vasculitis.)
  • Help distinguish between ulcerative colitis (UC) and Crohn disease (CD), two common types of inflammatory bowel disease (IBD).

ANCA are autoantibodies produced by a person's immune system that mistakenly attack proteins within the person's neutrophils (white blood cell types). The most common subsets of ANCA are those that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3).

Two types of tests may be used:

  • Most often, ANCA tests are performed using indirect immunofluorescence microscopy (IFA). Serum samples are mixed with neutrophils to allow autoantibodies that may be present to react with the cells. The sample is put on a slide and treated with a fluorescent stain. The slide is then examined under a microscope and the resulting pattern noted. The cytoplasmic pattern (cANCA) is associated with PR3 antibodies and the perinuclear pattern (pANCA) is associated with MPO antibodies. Another possible pattern is atypical ANCA.
  • Myeloperoxidase antibodies and proteinase 3 (PR3) antibodies may be individually and specifically tested using an immunoassay method.

Some laboratories will perform all three tests, ANCA, MPO and PR3, as a panel while others will perform MPO and PR3 only if an initial ANCA test is positive.

Additional tests that may be performed to aid in diagnosis include erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) to check for inflammation, complete blood count (CBC) to measure and evaluate white and red blood cells, and urinalysis, blood urea nitrogen (BUN), and creatinine to evaluate kidney function. For some patients, viral studies for hepatitis or cytomegalovirus may be ordered.

When is it ordered?

Vasculitis
An ANCA test and/or tests for MPO and PR3 are ordered when a person has signs and symptoms that suggest systemic autoimmune vasculitis. Early in the disease, symptoms may be vague or nonspecific, such as fever, fatigue, weight loss, muscle and/or joint aches, and night sweats. As the disease progresses, damage to blood vessels throughout the body may cause signs and symptoms associated with complications involving various tissues and organs. A few examples include:

  • Eyes – red, itchy eyes or "pink eye" (conjunctivitis); problems with sight (blurry vision, loss of vision)
  • Ears – hearing loss
  • Nose – runny nose or other upper respiratory symptoms that do not go away
  • Skin – rashes and/or granulomas
  • Lungs – cough and/or difficulty breathing
  • Kidneys –protein in the urine (proteinuria)

Testing may also be performed periodically to monitor a person who has been diagnosed with an autoimmune vasculitis.

Inflammatory Bowel Disease
An ANCA test may be ordered with a test for anti-Saccharomyces cerevisiae antibodies (ASCA) when a person has signs and symptoms that suggest inflammatory bowel disease and the health practitioner is attempting to distinguish between Crohn disease and ulcerative colitis.

Symptoms of an IBD may include:

  • Abdominal pain and cramps
  • Diarrhea
  • Rectal bleeding
  • Fever
  • Fatigue
  • In some people, joint, skin, bone, and organ-related symptoms
  • Children may also have delayed development and growth retardation.

What does the test result mean?

Results of ANCA tests must be interpreted carefully, taking several factors into account. A health practitioner will consider clinical signs and symptoms in addition to results of the laboratory tests and other types of tests, such as imaging studies.

Vasculitis

Positive ANCA, PR3, and/or MPO tests help to support a diagnosis of systemic autoimmune vasculitis and to distinguish between different types. However, to confirm a diagnosis, a biopsy of an affected site is often required.

Negative ANCA tests results mean it is unlikely that a person's symptoms are due to an autoimmune vasculitis.

For a positive result on the indirect immunofluorescence microscopy method, several different ANCA patterns may be seen:

  • Perinuclear (pANCA) - most of the fluorescence occurs near the nucleus. About 90% of samples with a pANCA pattern will have MPO antibodies.
  • Cytoplasmic (cANCA) - the fluorescence occurs throughout the cytoplasm of the cell. About 85% of samples with a cANCA pattern will have PR3 antibodies.
  • Negative ANCA – very little or no fluorescence

If an ANCA test result is positive, then an additional test is performed to determine the amount of antibody present. This is called a titer. To determine the titer, a Serum sample is diluted in steps and each dilution is tested for the presence of the antibody. The greatest dilution at which the antibody can be detected is the titer. For example, if a serum tests positive after being diluted 64-fold, the titer is 1:64. The higher the titer, the more antibody is present in the blood.

ANCA levels can change over time and may sometimes be used in a general way to monitor disease activity and/or response to therapy; however, titer levels may be inconsistent in some patients, poorly reflecting remission/relapse status.

In addition, tests that are specific for antibodies to MPO and PR3 may be performed:

  • A positive test for PR3 antibodies and a positive cANCA or pANCA are seen in more than 80% of patients with active granulomatosis with polyangiitis (Wegener granulomatosis).
  • A positive test for MPO antibodies and a positive pANCA are consistent with microscopic polyangitis, glomerulonephritis, eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome), and Goodpasture syndrome. MPO and pANCA may also be present in other autoimmune disorders, such as systemic lupus erythematosus, rheumatoid arthritis, and Sjogren syndrome.

The following table shows results that may be seen in some vasculitis conditions.

Condition % of patients with cANCA pattern (PR3 antibodies) % of patients with pANCA pattern (MPO antibodies)
Granulomatosis with polyangiitis (Wegener granulomatosis) 90% in active disease, 60-70% no active disease Less than 10%
Microscopic polyangiitis 30% 60%
Eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome) Rare 50-80%
Polyarteritis nodosa Rare Rare

Inflammatory Bowel Disease

ANCA testing can be useful in evaluating patients with symptoms of an inflammatory bowel disease (IBD).

  • If atypical ANCA is positive and ASCA (anti-Saccharomyces cerevisiae antibodies) is negative, then it is likely that the person has ulcerative colitis (UC).
  • If atypical ANCA is negative and ASCA is positive, then it is likely that the person has Crohn disease (CD). A person who is negative for ANCA and/or ASCA may still have UC, CD, or another IBD.

Is there anything else I should know?

In most cases, a biopsy of an affected blood vessel is necessary to confirm a diagnosis of autoimmune vasculitis.

Since the symptoms associated with vasculitis and inflammatory bowel disease may be seen with a number of conditions, other tests are frequently performed prior to or along with ANCA testing to rule out other causes for the symptoms.

What is being tested?

Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies produced by a person's immune system that mistakenly target and attack proteins within the person's neutrophils (a type of white blood cell). ANCA testing detects and measures the amount of these autoantibodies in the blood. Two of the most common types or subsets of ANCA are the autoantibodies that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3).

For the test, an individual's blood sample is mixed with neutrophils and the mixture is placed on a slide and treated with a fluorescent stain. If ANCA are present, they will produce a pattern of fluorescence that can be seen under a microscope. The pattern may be identified as cytoplasmic or cANCA, perinuclear (pANCA), or atypical ANCA (X-ANCA). Alternatively, the laboratory may test for myeloperoxidase antibodies or proteinase 3 antibodies directly using an ELISA assay. A combination of both fluorescence and ELISA tests are often done when working up suspected cases of vasculitis.

ANCA may be present in several autoimmune disorders that cause inflammation, tissue damage, and organ failure:

  • Systemic vasculitis is a group of disorders associated with damage and weakening of blood vessels. It can cause tissue and organ damage due to the narrowing and obstruction of blood vessels and the subsequent loss of blood supply. It can also produce areas of weakness in blood vessel walls, known as aneurysms, which have the potential to rupture. The symptoms experienced by a person with systemic vasculitis depend upon the degree of autoimmune activity and the parts of the body involved. A few types of systemic vasculitis are closely associated with the production of ANCA:
    • Granulomatosis with polyangiitis (Wegener granulomatosis)
    • Microscopic polyangiitis
    • Eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome)
    • Polyarteritis nodosa (PAN)
  • (For more information on these specific conditions, see the article on vasculitis).

    cANCA/PR3 antibodies are most frequently seen in granulomatosis with polyangiitis and pANCA/ MPO antibodies are most often associated with microscopic polyangiitis. However, both may be seen in all three types with varying degrees of reactivity.

  • Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) associated with swollen and damaged tissues in the lining of the colon. UC can be difficult to distinguish from Crohn disease (CD), another type of IBD that can affect any part of the intestinal tract. The presence of atypical ANCA is generally associated with UC (80% of patients), while only 20% of CD patients may be positive.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

  1. Will my antineutrophil cytoplasmic antibodies (ANCA) ever go away?

    Levels may fluctuate, but once a person has developed an autoantibody, that person will continue to have it.

  2. Can the ANCA test be performed at my doctor's office?

    ANCA testing requires specialized equipment and careful interpretation by trained professionals. Your sample will need to be sent to a clinical laboratory that performs these tests.

  3. Should everyone have an ANCA test done?

    ANCA testing is only necessary when a person has symptoms that suggest systemic vasculitis or inflammatory bowel disease (IBD). Most people will never need to have an ANCA test performed.

  4. Are there conditions other than vasculitis and inflammatory bowel disease that can cause a positive ANCA?

    Yes. These conditions include rheumatoid arthritis, systemic lupus erythematosus (SLE), pulmonary conditions, autoimmune hepatitis, use of certain drugs, and infections involving the heart (endocarditis) or the respiratory system.

  5. How many autoimmune disorders cause systemic vasculitis?

    There are many autoimmune disorders that have been identified (see the article on Vasculitis or the Related Pages tab for more on these). They are organized, with some overlap, by the size of the blood vessels that they affect - small, medium, or large.