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Proteinase-3 Antibody

Also Known As: Antineutrophil cytoplasmic antibodies (ANCA), Myeloperoxidase (MPO),  

What Is The Test?

It is defined as a test that analyses autoimmune diseases such as vasculitis, Wegener's Granulomatosis (WG), Microscopic Polyangiitis (MPA), and others. Proteinase 3 (PR3) antigen is a protein present in human neutrophils. Eventually, it's difficult to differentiate Wegener's Granulomatosis and other vasculitis forms based on clinical symptoms. So tests for Proteinase 3 (PR3) ANCA are done with other serologic tests to make the initial diagnosis.

The proteinase 3 (PR3) and Myeloperoxidase(MPO) are the enzymes present in the granules of neutrophils and work as an antigen for antineutrophil cytoplasmic antibodies (ANCA) in granulomatosis with polyangiitis. In case of injury, the mature PR3 enzyme exposes to the membrane through translocation resulting in the confirmation of disease.

ANCA profile test

Antineutrophil cytoplasmic antibodies (ANCA) are abnormally produced antibodies that attack the patient's neutrophil's cytoplasm. It has two subsets known as MPO 
and PR3; their appearance shows specific diseases.

ANCA test has two types; c-ANCA & p-ANCA used to differentiate the autoimmune disease.

  • c-ANCA/MPO/p-ANCA positivity mainly refers to microvascular polyangiitis.
  • PR3/p-ANCA/c-ANCA positivity mainly refers to Wegener's Granulomatosis (WG)

Some laboratories refer to the three tests, ANCA, MPO, and PR3, as a panel. But some lab testing for initial observation performs ANCA; if it gets positive, they opt for others such as MPO and PR3.

What Is The Test Used For?

The "Proteinase-3 Antibody" (PR3) Test is used to determine the following diseases:

Granulomatosis with polyangiitis or Wegener's granulomatosis (WG): is a disorder due to injury or inflammation caused in the blood vessel such as the sinuses, nose, throat, lungs, and kidneys.

Microscopic polyangiitis(MPA): is a rare type of inflammation in the small blood vessels. Mostly observed in elder age; however, there is no age limit.

Eosinophilic granulomatosis with polyangiitis or Churg-Strauss Syndrome (CSS): is characterized by swelling in specific tissues and blood. A patient with this disease mainly seems to be suffering from asthma or hypersensitive history. 

The test also diagnoses long-term fever, muscle pain, and autoimmune disorders such as ulcerative colitis, viral infection, and cirrhosis.

Why And When Do You Need To Get Tested?

Suppose that you suffer from long-term fever, muscle pain, or when your healthcare provider thinks you have "vasculitic"/ chest or kidney associated symptoms due to vascular inflammation disorder. The doctor, for further investigation, will say to get tested. 

Early-stage symptoms include specific or nonspecific:

  • Fever
  • Muscle and joint aches
  • Fatigue
  • Weight loss
  • Night sweats

Proceeding disease can damage small blood vessels in the body with several complications, including:

  • Red itchy eyes
  • Blurred vision
  • loss of vision
  • Hearing issues
  • Runny nose or other associated sensitivities
  • Rashes or granulomas
  • Lungs — breathing difficulties
  • Kidneys — abnormal protein production in the urine

Another case is when you are known to have antineutrophil cytoplasmic antibodies (ANCA) associated with small-vessel vasculitis; upon doctors' recommendations, a patient needs to get tested and monitored.

What Kind Of Sample Is Required?

Just a blood sample from the patient's arm is required. In some cases, a biopsy is needed as a sample to detect autoimmune vasculitis in any affected blood vessel.

Do You Need To Prepare For The Test?

No, you don't need to be prepared for the test. The test is done at any time according to your healthcare provider's recommendation.

Are There Any Risks To This Test?

You may face little bruising or pain while having a blood test where the needle was inserted. It's just a temporary pain. But laboratories should ensure to use of sterile needles to avoid internal infection. Further, there is no such risk associated with the test.

What Does The Test Result Mean?

The results of ANCA testing must be carefully evaluated, taking into consideration several parameters. When making a diagnosis, a health care provider will assess clinical signs and symptoms and the findings of other tests such as imaging examinations.

ANCA/PR3/MPO tests are done to diagnose systemic autoimmune vasculitis and to differentiate what type of it you have. A biopsy of the targeted area is done to determine the type of autoimmune vasculitis. 

After a sample has been analyzed and shown to be positive for MPO or PR3, ANCA tests are usually performed using indirect immunofluorescence microscopy. Serum samples are mixed with neutrophils to allow any present autoantibodies to bind to the cells. The material is placed on a slide and stained fluorescently. The pattern is then documented once the slide has been studied under a microscope.

Several patterns ANCA to confirm diagnosis patterns seen:

  • The fluorescence is cytoplasmic (c-ANCA) and occurs throughout the cell's cytoplasm. PR3 antibodies will be found in about 85% of samples with a c-ANCA pattern.
  • Negative ANCA shows no fluorescence.
  • Atypical p-ANCA is observed in ulcerative colitis, Crohn's disease, and rheumatoid arthritis patients.

According to international guidelines, The laboratories perform ANCA IIF on samples screened and positive for MPO/PR3;

The PR3/c-ANCA/p-ANCA positive results in active granulomatosis with polyangiitis. Positive MPO/p-ANCA is associated with the following:

MPO or p-ANCA positivity is also due to nonspecifically other autoimmune disorders, such as:


The additional tests that help to make a diagnosis include:

 ESR (erythrocyte sedimentation rate) is used to determine the inflammation.
 FBC (full blood count) analyses and evaluates white and red blood cells.
Creatinine test used to evaluate kidney function.  

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