Interpreting ANCA
PR3 and MPO immunoassays as the first-line test (2017 consensus), who should be tested, what a positive result means in GN, lung haemorrhage or sinus disease, the mimics (endocarditis, drugs, levamisole-cut cocaine, IBD), double positivity with anti-GBM, and why a rising titre alone isn't treated.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- PR3 and MPO immunoassays are the test. The 2017 international consensus dropped indirect immunofluorescence (IIF) as a mandatory first step because modern immunoassays perform as well or better.
- Test when pretest probability is meaningful. In a patient with GN, lung haemorrhage or destructive sinus disease, a positive PR3 or MPO is highly specific for ANCA-associated vasculitis (AAV). In unselected patients, false positives outnumber true ones.
- A positive result in rapidly progressive GN with an unstable patient justifies starting treatment while arranging biopsy.
Loading the rest of the note…
Finished reading?
Sources
- Therapeutic Guidelines: Rheumatology (systemic vasculitis)AU/NZTherapeutic Guidelines Limited, current online version, accessed November 2026
- RCPA Manual: antineutrophil cytoplasmic antibodies (ANCA), PR3 and MPO antibodiesAU/NZRoyal College of Pathologists of Australasia, online, accessed November 2026
- Bossuyt X et al. Position paper: Revised 2017 international consensus on testing of ANCAs in granulomatosis with polyangiitis and microscopic polyangiitis. Nat Rev Rheumatol 2017;13:683-92Nature Reviews Rheumatology, 2017 (no later revision found, November 2026)
- KDIGO 2024 Clinical Practice Guideline for the Management of ANCA-Associated Vasculitis. Kidney Int 2024;105(3S):S71-S116Kidney Disease Improving Global Outcomes (KDIGO), 2024
- Biddle K et al. The 2025 British Society for Rheumatology management recommendations for ANCA-associated vasculitis. Rheumatology (Oxford) 2025;64:4470-94British Society for Rheumatology, 2025
- Hellmich B et al. EULAR recommendations for the management of ANCA-associated vasculitis: 2022 update. Ann Rheum Dis 2024;83:30-47EULAR, 2022 update
- Kumar B et al. Hydralazine-associated vasculitis: overlapping features of drug-induced lupus and vasculitis. Semin Arthritis Rheum 2018;48:283-7Seminars in Arthritis and Rheumatism, 2018
- Jayne DRW et al. Avacopan for the treatment of ANCA-associated vasculitis (ADVOCATE). N Engl J Med 2021;384:599-609. Retracted 29 June 2026 (retraction notice doi:10.1056/NEJMe2608684)New England Journal of Medicine, 2021; retracted 2026
- Robson JC et al. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for granulomatosis with polyangiitis. Ann Rheum Dis 2022;81:315-20ACR and EULAR, 2022
- Suppiah R et al. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for microscopic polyangiitis. Ann Rheum Dis 2022;81:321-6ACR and EULAR, 2022
- Grayson PC et al. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for eosinophilic granulomatosis with polyangiitis. Ann Rheum Dis 2022;81:309-14ACR and EULAR, 2022
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Personal emails, About story and Australian-style copy