Blood draw
ANCA (anti-neutrophil cytoplasmic antibodies)
ANCA; vasculitis serology.
€ 69,00
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Inflammation and immunity · Blood
PR3-ANCA
Antibody against the body's own enzyme proteinase 3; part of testing for vasculitis, inflammation of small blood vessels.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
PR3-ANCA: what is measured?
PR3-ANCA is an autoantibody: an antibody that the body makes against its own tissue. The target is proteinase 3 (PR3), an enzyme in the granules of neutrophil granulocytes, a type of white blood cell. ANCA is the collective name for antibodies against those granules; PR3 and MPO are the two forms that matter in practice. According to the Dutch medical specialists' guideline (FMS) on small vessel vasculitis, the laboratory first screens with an immunofluorescence test and then uses an antigen-specific test to determine which of the two it is.
What can it detect?
- Support when granulomatosis with polyangiitis (formerly Wegener's disease) is suspected, a vasculitis that mainly affects the nose, sinuses, lungs and kidneys
- Support when another vasculitis of the small blood vessels is suspected
- Antibodies that also occur with a long-lasting infection, such as inflammation of a heart valve, and with certain medicines
Result
What does the result mean?
Positive result
A positive PR3-ANCA means that antibodies against proteinase 3 were found. That is not a diagnosis in itself. In someone with symptoms that fit vasculitis, such as sinuses that just won't heal, a saddle nose, coughing up blood, blood in the urine or rapidly worsening kidney function, a positive result makes granulomatosis with polyangiitis more likely. Without such symptoms, a positive result more often fits something else, for example a long-lasting infection or a medicine. A tissue examination is usually needed for the diagnosis.
Negative result
A negative result means that no antibodies against proteinase 3 were found. The chance that symptoms are due to an ANCA-associated vasculitis is then smaller. The disease is not completely ruled out: some people with such a vasculitis have only MPO-ANCA or no detectable ANCA at all. The result can also become negative after successful treatment.
After an abnormal result
With a positive result together with matching symptoms, the GP refers to an internist (specialist in internal medicine), rheumatologist, ENT specialist or nephrologist. This is usually followed by tests of the urine and kidney function, imaging of the lungs and sinuses, and often a biopsy to confirm the diagnosis. With a positive result without symptoms, treatment is generally not started.
Reliability
How reliable is the test?
The result is mainly meaningful with symptoms that fit vasculitis. The predictive value depends strongly on how high the chance of the disease already was beforehand: in people without matching symptoms, that chance is very small, and then a positive result is far more often false-positive than correct. According to the Dutch medical specialists' guideline (FMS) on small vessel vasculitis, a result only has meaning if both the immunofluorescence test and the antigen-specific test are positive. A result cannot be interpreted separately from the clinical picture.
What can affect the result?
- A positive ANCA also occurs without vasculitis, including with chronic inflammatory bowel disease, autoimmune hepatitis, a long-lasting infection such as endocarditis, and with the use of medicines such as propylthiouracil, hydralazine and levamisole-contaminated cocaine.
- According to the Dutch medical specialists' guideline (FMS), only results that are positive in both the immunofluorescence test and the antigen-specific test count; if only one of the two tests is positive, the predictive value drops sharply.
- If there are also antinuclear antibodies (ANA) in the blood, the P-ANCA pattern in the immunofluorescence test may be hard to read.
- Laboratories use different methods and cut-off values; results from different labs cannot simply be compared.
Who it is for
Who is the test useful for?
Useful for
Useful with a specific suspicion of vasculitis of the small blood vessels: sinus or ear infections that do not go away, crusts and bleeding in the nose, coughing up blood, blood in the urine, a skin rash with small bleeds, loss of nerve function or unexplained fever with weight loss. In people without such symptoms, the test adds nothing and the chance of a result that fits nothing is greater than the chance of a disease.
How common is it?
Vasculitis of the small blood vessels is rare. In Northern Europe, an estimated 1 to 2 new cases per 100,000 inhabitants occur each year, mainly in people over 50. A positive ANCA result is more common than the disease itself, because other conditions and medicines can also produce antibodies.
Estimate from European epidemiological research; the FMS guideline on small vessel vasculitis gives no Dutch incidence figure
Drawbacks and risks
- In people without symptoms, a positive result is more often false-positive than correct. This can lead to unnecessary worry about a serious disease and to further tests, such as a biopsy, that would not have been needed without symptoms.
- A negative result does not rule out vasculitis and can therefore give false reassurance if there are symptoms.
Get tested
PR3-ANCA: test panels
PR3-ANCA is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and results- NVKC, allesovertesten.nl: ANCA
- FMS Richtlijnendatabase: Kleine vaten vasculitis, module Volgorde ANCA-testen bij vasculitis
- FMS Richtlijnendatabase: Kleine vaten vasculitis, module Beoordeling ANCA voor diagnose vasculitis
- FMS Richtlijnendatabase: Kleine vaten vasculitis, korte beschrijving
- NVKC, allesovertesten.nl: Autoantilichamen
More explanations
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