What is the Myeloperoxidase Antibodies test?

The Myeloperoxidase (MPO) Antibodies test measures antibodies directed against myeloperoxidase, an enzyme found inside neutrophils (a type of white blood cell). These antibodies are part of the ANCA (anti-neutrophil cytoplasmic antibody) group and are typically referred to as p-ANCA (MPO-ANCA).

MPO antibodies are strongly associated with certain autoimmune conditions that cause inflammation of small blood vessels. The test is an important tool in diagnosing and monitoring ANCA-associated vasculitis, particularly when symptoms involve the kidneys, lungs, skin, or nervous system.

Why do I need a Myeloperoxidase Antibodies test?

Autoimmune vasculitis can present with vague or multisystem symptoms and may cause serious organ damage if not identified early.

You may need this test if you experience:

• Persistent unexplained fatigue

• Kidney abnormalities (blood or protein in urine)

• Shortness of breath or coughing up blood

• Skin rashes or purpura

• Joint or muscle pain

• Nerve symptoms such as numbness or weakness

• Unexplained inflammation markers

• Suspected autoimmune disease affecting multiple organs

The test helps determine whether symptoms are driven by immune-mediated blood vessel inflammation.

Benefits of the test

1. Key marker of autoimmune vasculitis
   Strongly linked to MPO-ANCA conditions.

2. Supports early diagnosis
   Helps identify disease before irreversible damage.

3. Guides further specialist investigation
   Supports referral and imaging decisions.

4. Clarifies cause of systemic inflammation
   Distinguishes autoimmune from infectious causes.

5. Simple blood-based testing
   Requires only one blood sample.

6. Widely used in rheumatology and nephrology
   Standard ANCA marker.

7. Supports disease monitoring
   May be used alongside clinical assessment.

8. Improves diagnostic confidence
   Reduces uncertainty in complex presentations.

Step-by-step: How we offer testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic

• Attend your appointment

• Blood sample taken by a clinician

• Sample sent to the laboratory

• Results issued once analysis is complete

Home or hotel visit (+£60, UK-wide)

• Mobile phlebotomist attends your location

• Blood sample taken at home or hotel

• Sample securely transported to the laboratory

Your results explained

Negative MPO antibodies

• No MPO antibodies detected

• UK standard: Negative

• Makes MPO-associated vasculitis less likely

Low to moderate positive

• MPO antibodies detected at low or moderate level

• UK standard: Positive (low/moderate)

• May indicate early or limited autoimmune activity

High positive

• Significantly elevated MPO antibodies

• UK standard: High positive

• Strongly suggests active ANCA-associated vasculitis

Results should always be interpreted alongside symptoms, other ANCA tests, and clinical findings.