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What is an Anti-Neutrophil Cytoplasmic Antibody (ANCA) profile test?

ANCAs are autoantibodies produced against certain proteins present in neutrophils, a type of white blood cell. An ANCA test is used to detect the presence of these autoantibodies in your blood. 

The two most common types of neutrophil proteins that are targetted by these autoantibodies are myeloperoxidase (MPO) and proteinase 3 (PR3). So, to identify the specific type of ANCA, MPO and PR3 tests are suggested in case ANCA test results come out to be positive. All three tests are performed together in some cases.

The test can be of two types:

  • Direct immunofluorescence microscopy
  • Immunoassay method
  1. How do you prepare for an ANCA Profile test?
  2. How is an ANCA Profile test performed?
  3. Why is an ANCA Profile test performed?
  4. What do ANCA Profile test results indicate?

No special preparation is needed for this test.

A lab-technician will withdraw a blood sample from a vein in your arm and collect it in a sterile vial or a test tube for further analysis. He/she will then press the injection site firmly and place a cotton ball or gauze pad over that area to prevent bleeding. 

Light-headedness and bruising at the site of injection are some common effects of this test. However, at most times, these symptoms disappear quickly. Rarely, an infection may occur at the site of withdrawal of blood.

This test is done to diagnose forms of autoimmune systemic vasculitis (characterised by blood vessel inflammation).

Common signs and symptoms of the condition include:

Your doctor may suggest an ANCA Profile test if he/she notices the following symptoms with a probability of an autoimmune condition:

It can also be used to distinguish between the two most common types of inflammatory bowel diseases (IBD): Crohn’s disease (CD) and ulcerative colitis (UC)

Other tests that are usually suggested along with ANCA are:

Results should be interpreted after taking all the clinical signs and symptoms into consideration. The final diagnosis is based on other parameters, including additional laboratory tests and imaging studies.

For vasculitis:

  • Positive results for ANCA, MPO and PR3 indicate the presence of systemic autoimmune vasculitis. It also helps identify the type of vasculitis. A biopsy will further confirm the diagnosis
  • Negative results suggest that the clinical symptoms are not related to the presence of systemic autoimmune vasculitis

Various patterns can be seen in a positive result for indirect immunofluorescence microscopy method:

  • Perinuclear ANCA (pANCA): Maximum fluorescence is seen around the nucleus. MPO antibodies will be present in around 90% of the pANCA pattern
  • Cytoplasmic ANCA (cANCA): Maximum fluorescence is scattered throughout the cytoplasm. PR3 antibodies can be found in 80% of the cANCA pattern
  • Negative ANCA: It shows very less or no fluorescence

In addition, an antibody titre test is performed for measuring the level of antibodies in blood only if ANCA test results are positive. The sample is continuously diluted in steps, and at each dilution, the presence of Anti-Neutrophil Cytoplasmic Antibody is checked. The highest dilution at which the antibody is detected is called titre. A higher titre indicates a higher number of antibodies present.

Test specific for antibodies to MPO and PR3 have the following results:

  • Positive PR3 and pANCA or cANCA are indicative of granulomatosis with polyangiitis (Wegener granulomatosis).
  • Positive MPO antibodies and pANCA are indicative of Good pasture syndrome, glomerulonephritis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome).

ANCA test for IBD:

  • UC is a more likely the diagnosis if the ANCA assay is positive and anti-Saccharomyces cerevisiae antibodies assay (ASCA) is negative
  • CD is a more likely the diagnosis when ANCA results are negative and ASCA results are positive
  • If the results of ANCA and ASCA tests are both negative, the individual could have UC, CD or other IBD

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor. 

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References

  1. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Granulomatosis with Polyangiitis
  2. Johns Hopkins Medicine [Internet]. The Johns Hopkins Vasculitis Center, The Johns Hopkins Hospital, and Johns Hopkins Health System; Microscopic Polyangiitis
  3. The royal college of pathologists of australia. Antineutrophil cytoplasmic antibody, ANCA. Australia. [internet].
  4. National Center for Advancing Translational Sciences [internet]: US Department of Health and Human Services; ANCA-associated vasculitis
  5. Radice A, Sinico RA. Antineutrophil cytoplasmic antibodies (ANCA).. Autoimmunity. 2005 Feb;38(1):93-103. PMID: 15804710