ANCA/MPO/PR3 Antibodies
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
The ANCA/MPO/PR3 antibodies test is a blood test in which a sample is taken from a vein and analysed to detect anti-neutrophil cytoplasmic antibodies including PR3 and MPO in the bloodstream. It is used to help support a diagnosis of systemic autoimmune vasculitis and to distinguish between different types of these inflammatory blood vessel disorders by identifying specific antibody patterns.
Why get tested?
To test for certain autoimmune disorders, specifically small vessel vasculitides such as as Granulomatosis with polyangitis (GPA formerly known as Wegner’s Granulomatosis [WG]), microscopic polyangitis (MPA), Eosinophilic Granulomatosis with Polyangitis (EGPA formally known as Churg-Strauss Syndrome) and a few others.
When to get tested?
When your doctor thinks that you have symptoms, such as a “vasculitic” rash or chest/kidney symptoms that may be due to a vascular inflammatory disorder; In patients who are known to have antineutrophil cytoplasmic antibodies (ANCA) associated small vessel vasculitis, ANCA measurement is sometimes used to monitor response to therapy
Sample required?
A blood sample taken from a vein in your arm
Test preparation needed?
None
What is being tested?
Antineutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies produced when a person’s immune system mistakenly targets and attacks its own neutrophil proteins. Two of the most commonly targeted proteins are myeloperoxidase (MPO) and proteinase 3 (PR3). This results in the production of antibodies to MPO and/or PR3. The ANCA blood test detects the presence or absence of these autoantibodies by looking for the presence of these antibodies by an ELISA test and may also look to confirm these by the pattern of fluorescence on a slide under a microscope.
Antineutrophil cytoplasmic antibodies may be present in a variety of autoimmune disorders that cause inflammation and damage to blood vessels, predominantly small blood vessels, throughout the body (systemic vasculitis). Vasculitis can cause tissue and organ damage due to the narrowing and obstruction of these small 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 small vessel systemic vasculitis depend upon the degree of autoimmune activity and the parts of the body involved. Early in the disease process, symptoms are often nonspecific – they include fatigue, fever, weight loss, muscle aches, and night sweats. As the disorder progresses, vascular damage may affect the functioning of the kidneys, eyes, skin, lungs, and liver. This can cause a wide range of symptoms related to these organ systems.
PR3 antibodies are most frequently seen in Granulomatosis with polyangitis (GPA). MPO antibodies are most often associated with microscopic polyangitis but may also be seen in people with pauci-immune necrotising glomerulonephritis, and eosinophilic granulomatosis with polyangiitis (EGPA).For more about these conditions, visit the Vasculitis UK.
Common questions
An ANCA test is requested in order to evaluate someone who has symptoms that may be due to autoimmune vasculitis. It may be requested by itself or along with two other tests that are used to distinguish between different autoimmune disorders. The current recommendation is that a laboratory tests specifically for MPO and PR3 antibodies and confirms new positives as appropriate. Most people still call the MPO and PR3 antibody tests an ANCA test.
Additional tests that may be performed to aid in a diagnosis include ESR (erythrocyte sedimentation rate) to check for inflammation, FBC (full blood count) to measure and evaluate white and red blood cells, complement levels to assess inflammation and creatinine to evaluate kidney function. Sometimes an ANCA test may be requested to monitor the response to therapy, follow the course of the disease, and/or to detect a relapse.
An ANCA test or tests for MPO and PR3 are requested when a person is suspected of having a systemic autoimmune vasculitis, especially when symptoms suggest Granulomatosis with polyangitis (GPA ) or microscopic polyangiitis. 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 small 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, nasal bleeding and crusting that is otherwise unexplained
- Skin — rashes and/or granulomas
- Lungs — cough and/or difficulty breathing
- Kidneys — abnormal amounts of protein in the urine
Some laboratories will perform all three tests MPO and PR3 followed by ANCA immunoflouresence as a panel while others will perform MPO and PR3 only.
Testing may also be performed periodically to monitor a person who has been diagnosed with an autoimmune vasculitis.
Results of ANCA tests must be interpreted carefully and take several factors into account. A doctor will consider clinical signs and symptoms and results of other types of tests such as imaging studies when determining a diagnosis.
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 most often required. Negative tests results make it much less likely that a person’s symptoms are due to an autoimmune vasculitis.
Most often, ANCA tests are performed using indirect immunofluorescence microscopy after a sample has been tested and is positive for MPO or PR3. 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.
Several different ANCA patterns may be seen:
- Perinuclear (p‑ANCA) – most of the fluorescence occurs near the nucleus. About 90% of samples with a p‑ANCA pattern will have MPO antibodies.
- Cytoplasmic (c‑ANCA) – the fluorescence occurs throughout the cytoplasm of the cell. About 85% of samples with a c‑ANCA pattern will have PR3 antibodies.
- Negative ANCA — very little or no fluorescence
- Atypical p‑ANCA — seen in many cases of ulcerative colitis as well as some patients with Crohn’s disease and rheumatoid arthritis.
The majority of laboratories will follow the new international guidance and the ANCA IIF will only be performed on samples already screened and known to be positive for MPO or PR3;
- A positive test for PR3 antibodies and a positive c‑ANCA or p‑ANCA are seen in more than 80% of patients with active GPA
- A positive test for MPO antibodies and a positive p‑ANCA are consistent with microscopic polyangitis, glomerulonephritis, Eosinophilic Granulomatosis with polyangitis, and Goodpasture’s syndrome. MPO and p‑ANCA may also be present non specifically in other autoimmune disorders, such as systemic lupus erythematosus, rheumatoid arthritis, and Sjögren syndrome.
The following table shows results that may be seen in some vasculitis conditions.
| Condition | % of patients with c‑ANCA pattern (PR3 antibodies) | % of patients with p‑ANCA pattern (MPO antibodies) |
| Granulomatosis with polyangitis (GPA) | 90% in active disease, 60–70% no active disease | Less than 10% |
| Microscopic polyangiitis | 30% | 60% |
| Eosinophilic Granulomatosis with polyangiitis (EGPA) | Rare | 50–80% |
| Polyarteritis nodosa | Rare | Rare |
ANCA levels can change over time and may sometimes be used in a general way to monitor disease activity and/or response to therapy.
In most cases, a biopsy of an affected tissue is necessary to confirm a diagnosis of autoimmune vasculitis.
Levels may fluctuate, but once a person has developed an autoantibody, they will continue to have it.
ANCA, MPO and PR3 tests require specialised equipment. Your sample will need to be sent to a clinical immunology laboratory that performs these tests.
ANCA testing is only necessary when a person has symptoms that suggest systemic vasculitis. Most people will never need to have an ANCA test performed.
Yes, there are several. Some of these include rheumatoid arthritis, inflammatory bowel disease, certain drugs, and infections involving the heart (endocarditis) or the respiratory system. The presence of a positive ANCA in these diseases does not mean that the patient has small vessel vasculitis.
There is quite a long list of autoimmune disorders that have been identified (see the Links tab for more on these). They are organised, with some overlap, by the size of the blood vessels that they affect – small, medium, or large.