ANCA : Antineutrophil Cytoplasmic Antibodies test

🏾 Content :

• Definition
• Why the ANCA blood test is performed?
• Blood sample for ANCA test
• ANCA test
• Interpretation of results
• What other tests could I have with this test?
• Frequently Asked Questions

🏾 Why the ANCA blood test is performed ?

ANCA detection is a well-established diagnostic test for the evaluation of patients suspected of having AAV and certain inflammatory bowel diseases.

Autoimmune vasculitides cause inflammation and swelling of small blood vessels. These tiny blood vessels are found all over the human body, so any part of the body can be affected, but most commonly the kidneys, lungs, joints, ears, nose, and nerves.

Organs	Symptoms
General symptoms	Fever, Fatigue, Weightloss, Muscle and/or joint pain.
The eyes	Redness, Blurred vision, Loss of vision.
The ears	Ringing in the ears (tinnitus), Hearing loss.
The sinuses	Sinus pain, Runny nose, Nosebleeds.
The skin	Rashes, Wounds or ulcers, a type of deep wound that is slow to heal and/or keeps coming back.
The lungs	Cough, Difficulty breathing, Chest pain.
The kidneys	Blood in the urine, Foamy urine, which is caused by protein in the urine

Each type of ANCA affects different blood vessels and parts of the body. Types of autoimmune vasculitis include:

• Granulomatosis with polyangiitis (formerly called Wegener's granulomatosis): This most commonly affects the lungs, kidneys and sinuses.
• Microscopic Polyangiitis (MPA): This disorder can affect multiple organs in the body, including the lungs, kidneys, nervous system, and skin.
• Eosinophilic granulomatosis with polyangiitis (formerly called Churg-Strauss syndrome): This disorder usually affects the skin and lungs. It often causes asthma.

🏾 Blood sample for ANCA test

ANCAs are detected using a simple blood sample. There are no special preparations to make before the analysis and does not require fasting, unless your blood sample will be used for additional testing.

🏾 ANCA test

Indirect immunofluorescence (IFI) and enzyme immunoassay (ELISA) are the most commonly used techniques for detecting ANCA.

Indirect immunofluorescence (IFI)

uses ethanol-fixed neutrophils on a slide (5 minutes at +4 ◦C with ethanol 96-99%). The serum from your blood sample is mixed with the neutrophils on the slide and all the ANCAs in the sample attach to the neutrophil proteins. Treatment of the slide with a fluorochrome-stained antibody reacts with any ANCA present.

The two most common major immunostaining patterns are designated by the acronyms C-ANCA and P-ANCA:

• The granular cytoplasmic pattern with central emphasis, known as C-ANCA.
• The perinuclear pattern, which is defined as perinuclear fluorescence with nuclear extension and known as P-ANCA.

Note:
- A third aspect, described last and which is the most debated, is called atypical (aANCA), and combines characteristics of first two - If an ANCA test result is positive, an additional step may be taken to determine the amount of antibodies present. This is called a title

ELISA

The typing of the two main specificities (myeloperoxidase and proteinase 3) will be done by ELISA. This type of test helps identify the targeted protein in neutrophils.

🏾 Results interpretation

◾ ANCA test results should be interpreted with caution considering several factors. Your doctor will review your signs and symptoms in addition to the results of lab tests and other types of tests, such as imaging studies

Status	% of patients with cANCA profile (PR3 antibodies)	% of patients with pANCA profile (MPO antibodies)
Granulomatosis with polyangiitis (Wegener's granulomatosis)	90% with active disease, 60-70% without active disease	Less than 10%
Microscopic polyangiitis	30%	60%
Eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome)	Rare	50-80%
Polyarteritis nodosa	Rare	Rare

ANCA levels can change over time and can sometimes be used generally to monitor disease activity and/or response to treatment.

◾ In case of suspected inflammatory bowel disease (IBD):

• If ANCA is positive and ASCA (anti-Saccharomyces cerevisiae antibody) is negative, you are likely to have ulcerative colitis
• If ANCA is negative and ASCA is positive, you are likely to have Crohn's disease

🏾 What other tests could I have with this test?

Additional tests that may be performed to aid in diagnosis: erythrocyte sedimentation rate (ESR), CRP, Complete blood count (CNF), Blood urea nitrogen (BUN) concentration and creatinine to assess kidney function...

🏾 Frequently Asked Questions

Q: In which laboratories carry out ANCA research?

A: ANCA tests require specialized equipment and careful interpretation by trained professionals. Results may take several days to a week.

Q: How to differentiate between true pANCA antibodies from possible interference with antinuclear antibodies (ANA)?

A: Sera from positive patients with perinuclear or nuclear patterns are replicated using a formalin-fixed substrate, as well as methanol, to differentiate them

Q: Will anti-neutrophil cytoplasmic antibodies (ANCA) ever disappear?

A: Like other autoimmune diseases, levels can fluctuate, but once you develop an autoantibody, you will continue to have it.

Q: What are the different fixers used?

R: Ethanol, Formalin, Methanol