What are the other Names for this Test? (Equivalent Terms)
- Anti-Neutrophil Cytoplasmic Antibodies (ANCA) Test
- MPO-ANCA Test
- Serine Protease 3 Test
What is ANCA/MPO/PR3 Antibodies Test? (Background Information)
- ANCA/MPO/PR3 Antibodies Test is used in the detection of a number of abnormalities that are caused due to the body’s overactive immunity system attacking cells and tissues of the human body
- When the body’s immune system attacks its own cells and tissues, it causes autoimmune disorders. Such an attack would lead to the formation of abnormal antibodies
- The autoimmune disorders include Wegener's granulomatosis (a very rare disorder) and microscopic polyangiitis
What are the Clinical Indications for performing the ANCA/MPO/PR3 Antibodies Test?
An Anti-Neutrophil Cytoplasmic Antibodies (ANCA) Test is usually ordered along with two other tests, in order to distinguish between different kinds of autoimmunity disorders, especially when inflammation of the blood vessels, termed as vasculitis, is suspected. The 2 tests are:
- Myeloperoxidase (MPO) Antibodies Test and
- Proteinase 3 (PR3) Antibodies Test
The group of tests may be ordered for the following reasons:
- When an individual has signs and symptoms of autoimmune disorders, such as:
- Vision problems; red, itchy eyes
- Runny nose, cough, breathing difficulties
- Loss of hearing
- Higher protein content in the urine, due to the kidney being affected
- The initial symptoms may be non-specific and these could include - fatigue, lethargy, fever, muscle aches and joint aches, and loss of weight. Most often, prominent signs and symptoms are observed, when blood vessels begin to get damaged
- This test also establishes the response of a patient to treatment and helps prevent the rise of further complications
How is the Specimen Collected for ANCA/MPO/PR3 Antibodies Test?
Sample required: Blood
Process: Insertion of needle into a vein (arm).
Preparation required: None
What is the Significance of the ANCA/MPO/PR3 Antibodies Test Result?
A set of diverse results may be observed and many ANCA patterns are noted, as an outcome of the immunofluorescence microscopic studies. Most ANCA Tests are performed using immunofluorescence microscopic technique. The results observed are:
- p-ANCA (perinuclear) pattern: MPO antibodies are present in 90% of the samples having this pattern; where the fluorescence crowds around the nucleus
- c-ANCA (cytoplasmic) pattern: PR3 antibodies are present in 85% of the samples having this pattern; where the fluorescence is spread throughout the cell cytoplasm
- Atypical p-ANCA pattern: Individuals suffering from ulcerative colitis exhibit this pattern, and in a few cases, those affected with Crohn’s disease and rheumatoid arthritis too show this pattern
- Negative ANCA: When hardly any fluorescence is observed
Nevertheless, in order to arrive at a conclusive decision the physician has to carefully observe signs and symptoms of the patient, check other diagnostic study results, including the ANCA Test result.
If PR3 antibodies and MPO antibodies tests are additionally performed for autoimmune disorders, then:
- A positive test result for PR3 antibodies and c-ANCA or p-ANCA could indicate:
- Active Wegener's granulomatosis in 80% of the cases
- A positive test result for MPO antibodies and p-ANCA could indicate with certainty, the following disorders:
- Microscopic polyangiitis
- Goodpasture's syndrome
- Churg-Strauss syndrome
- Systemic lupus erythematosus, rheumatoid arthritis, and Sjögren syndrome, are also known to show a positive outcome for MPO antibodies and p-ANCA
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Blood serum samples are combined with white blood cells (neutrophils) causing autoantibodies (if any), to react with the cells. These are then labeled with a fluorescent dye and observed under a microscope. This is called indirect immunofluorescence microscopy. Most ANCA Tests are performed using this particular technique
- If a positive test result for ANCA and PR3, and/or MPO antibodies is obtained, then a biopsy is performed to establish systemic autoimmunity disorders (vasculitis or other types).
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
The following article link will help you understand Wegener granulomatosis: