What Does a Positive ANCA Test Mean?

A positive ANCA test means your blood contains antineutrophil cytoplasmic antibodies, which mistakenly target neutrophils, a type of white blood cell. It can point towards a group of conditions called ANCA-associated vasculitis, where small blood vessels become inflamed. A positive result is not a diagnosis by itself; clinicians combine it with symptoms, other tests and sometimes a biopsy.

This guide is for adults reviewing a positive ANCA report. It explains the terms you may see and helps you prepare questions. It cannot tell you whether you have vasculitis or how urgent your situation is.

Some forms of vasculitis can affect the kidneys and lungs. Do not wait for a routine follow-up appointment if you notice warning signs. The NHS gives this advice for two important symptoms.

Coughing up more than a few spots or streaks of blood, or coughing blood with trouble breathing, a very fast heartbeat or chest pain, needs emergency care: call your local emergency number or go to an emergency department. Smaller streaks of blood in phlegm, or any blood in your urine, need an urgent medical appointment.

Also contact your clinician promptly about new or worsening symptoms linked with vasculitis.

• Pink, red or brown urine, or swelling in the legs.
• Shortness of breath or a cough that is getting worse.
• Nosebleeds, crusting in the nose or long-lasting sinus problems.
• New numbness, pins and needles or weakness.
• Fever, night sweats, weight loss without trying or a new rash.

Vasculitis means inflammation of blood vessels. The NHS describes it as ranging from a minor problem affecting only the skin to a serious illness affecting organs such as the kidneys. In the ANCA-associated types, small blood vessels are mainly affected, and NHLBI notes that GPA usually affects the nose and throat, lungs and kidneys.

The NHS lists general symptoms such as a high temperature, tiredness, weight loss and joint or muscle pain. GPA can also cause blocked or runny nose, nosebleeds, sinus pain, ear problems, red or sore eyes, a persistent cough and leg swelling. These symptoms are common and often have other causes, which is why a positive test and symptoms are assessed together rather than separately.

Many laboratories first screen for ANCA by looking at how a sample stains neutrophils under a microscope. A cytoplasmic pattern spread through the cell is called c-ANCA. A perinuclear pattern clustered around the nucleus is called p-ANCA. Cleveland Clinic notes that testing can show one type or both.

The pattern is a clue rather than an answer. The Oxford University Hospitals NHS laboratory notes that c-ANCA is usually linked with antibodies to PR3 and p-ANCA with antibodies to MPO, which is why most labs go on to test those specific antibodies.

PR3 stands for proteinase 3 and MPO for myeloperoxidase. These are proteins inside neutrophils, and a separate blood test measures antibodies against each one. Results are often given as a number with the lab's cut-offs for negative, equivocal and positive. Units and cut-offs differ between laboratories, so compare your value only with the range printed on your own report.

Cleveland Clinic and NHS laboratory guidance link these antibodies with specific conditions. They are associations, not certainties, and a clinician interprets them alongside your symptoms.

• PR3 (often c-ANCA): most often linked with granulomatosis with polyangiitis (GPA), which tends to affect the nose and sinuses, lungs and kidneys.
• MPO (often p-ANCA): more often linked with microscopic polyangiitis (MPA) and a kidney inflammation called pauci-immune glomerulonephritis.
• Eosinophilic granulomatosis with polyangiitis (EGPA) is another ANCA-associated condition. The NHS notes it can cause asthma and allergy-like nose symptoms.

Yes. ANCA can be found in people who do not have vasculitis. The Oxford NHS laboratory lists infective endocarditis, tuberculosis, non-Hodgkin lymphoma and AIDS as conditions that can produce a positive result and mimic vasculitis. A p-ANCA pattern can also appear in rheumatoid arthritis, lupus and ulcerative colitis.

For this reason, some laboratories only run the test when symptoms suggest small-vessel vasculitis, to reduce misleading results. NHLBI also notes that some medicines can trigger blood vessel inflammation, so bring a full list of prescription and non-prescription medicines and supplements to your appointment. Do not stop a prescribed medicine on your own because of an ANCA result.

The NHS says there is no single test for GPA and that diagnosis can be difficult. Cleveland Clinic says a positive ANCA result may lead to more blood tests or a biopsy, where a small piece of affected tissue is examined. NHS guidance also mentions X-ray, CT or MRI scans of affected areas, and urine tests if there are kidney symptoms.

For people already known to be ANCA-positive, laboratories such as Oxford's measure MPO or PR3 levels on later samples. Ask how your team plans to use any repeat result and what else they will check alongside it.

Bring the full report, including the pattern, the MPO and PR3 values and the lab's reference ranges.

• Was my result c-ANCA or p-ANCA, and were MPO or PR3 antibodies found?
• How strongly positive was it compared with this laboratory's cut-off?
• Do my urine and kidney blood tests show any sign of kidney involvement?
• Could an infection, another autoimmune condition or one of my medicines explain this result?
• Do I need a biopsy, imaging or a referral to rheumatology or kidney specialists?
• Which symptoms should make me seek help before my next appointment?

On SameCase, people and verified doctors share de-identified cases. Reading how others with a positive ANCA result described their symptoms, test sequence and specialist visits can help you work out what to ask and what records to bring.

Another person's path may be very different from yours, and we do not diagnose or predict outcomes. Use what you read to prepare questions, then discuss them with the clinician who knows your full results. If you also have a positive ANA, our separate guide on that result explains how it differs.