Blood draw
ANCA (anti-neutrophil cytoplasmic antibodies)
ANCA; vasculitis serology.
€ 69,00
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Inflammation and immunity · Blood
MPO-ANCA
Antibody against the body's own enzyme myeloperoxidase; part of testing for vasculitis, inflammation of small blood vessels.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
MPO-ANCA: what is measured?
MPO-ANCA is an autoantibody: an antibody that the body makes against its own tissue. The target is myeloperoxidase (MPO), an enzyme in the granules of neutrophil granulocytes, a type of white blood cell. ANCA is the collective name for antibodies against those granules; MPO and PR3 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 whether it is MPO-ANCA or PR3-ANCA.
What can it detect?
- Support when vasculitis of the small blood vessels is suspected, mainly microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
- A sign of kidney inflammation (glomerulonephritis) that goes with such a vasculitis
- Antibodies that also occur in other conditions, such as chronic bowel inflammation, autoimmune hepatitis or the use of certain medicines
Result
What does the result mean?
Positive result
A positive MPO-ANCA means that antibodies against myeloperoxidase were found. That is not a diagnosis on its own. In someone with symptoms that fit vasculitis, such as long-standing fever, weight loss, blood in the urine, coughing up blood or rapidly worsening kidney function, a positive result makes vasculitis of the small vessels more likely. Without such symptoms, a positive result more often fits something else: chronic bowel inflammation, a liver condition, a long-lasting infection or a medicine. The level of the result does not say how severe the disease is, and a tissue examination is usually needed for the diagnosis.
Negative result
A negative result means that no antibodies against myeloperoxidase were found. The chance that symptoms are caused by an ANCA-associated vasculitis is then smaller. The disease is not ruled out: a small proportion of people with such a vasculitis have no detectable ANCA, and in vasculitis of the large vessels the ANCA is negative by definition. 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 or nephrologist. There, testing of urine and kidney function, imaging and often a biopsy of the kidney, skin or nasal lining usually follow 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 informative 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 a positive result is then much 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 separate from the clinical picture cannot be interpreted.
What can affect the result?
- A positive ANCA also occurs without vasculitis, among other things in chronic bowel inflammation, autoimmune hepatitis, a long-lasting infection such as endocarditis and with use of medicines such as propylthiouracil, hydralazine and levamisole-contaminated cocaine.
- According to the FMS guideline, 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 not be readable properly.
- Laboratories use different methods and cutoff 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: symptoms such as persistent unexplained fever, weight loss, blood in the urine, inflamed sinuses that do not go away, coughing up blood, a skin rash with small bleeds or loss of nerve function. 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 the age of 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 Dutch medical specialists' guideline (FMS) 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 follow-up testing, 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 when there are symptoms.
Get tested
MPO-ANCA: test panels
MPO-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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