title: Development and validation of a consensus methodology for the classification of the ANCA-associated vasculitides and polyarteritis nodosa for epidemiological studies.
abstract: BACKGROUND
  The classification of antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and polyarteritis nodosa (PAN) for epidemiology studies is confusing. The existing schemes such as American College of Rheumatology (ACR) criteria, Chapel Hill Consensus Conference (CHCC) definitions and Lanham criteria produce overlapping and conflicting classifications, making it difficult to compare incidence figures.
  
  
  OBJECTIVE
  To develop a consensus method of using these criteria and definitions for epidemiological studies to permit comparison without confounding by classification.
  
  
  METHODS
  A stepwise algorithm was developed by consensus between a group of doctors interested in the epidemiology of vasculitis. The aim was to categorise patients with Wegener's granulomatosis, microscopic polyangiitis (MPA), Churg-Strauss syndrome (CSS) and PAN into single clinically relevant categories. The ACR and Lanham criteria for CSS, and ACR criteria for Wegener's granulomatosis were applied first, as these were considered to be the most specific. Surrogate markers for Wegener's granulomatosis were included to distinguish Wegener's granulomatosis from MPA. MPA was classified using the CHCC definition and surrogate markers for renal vasculitis. Finally, PAN was classified using the CHCC definition. The algorithm was validated by application to 20 cases from each centre and 99 from a single centre, followed by a paper case exercise.
  
  
  RESULTS
  A four-step algorithm was devised. It successfully categorises patients into a single classification. There was good correlation between observers in the paper case exercise (91.5%; unweighted kappa = 0.886).
  
  
  CONCLUSIONS
  The algorithm achieves its aim of reliably classifying patients into a single category. The use of the algorithm in epidemiology studies should permit comparison between geographical areas.
authors.affiliation: Department of Rheumatology, Ipswich Hospital NHS Trust, Heath Road, Ipswich IP4 5PD, UK. richard.watts@ipswichhospital.nhs.uk
authors.forename: Richard
authors.initials: R
authors.lastname: Watts
authors.forename: Suzanne
authors.initials: S
authors.lastname: Lane
authors.forename: Thomas
authors.initials: T
authors.lastname: Hanslik
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauser
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hellmich
authors.forename: Wenche
authors.initials: W
authors.lastname: Koldingsnes
authors.forename: Alfred
authors.initials: A
authors.lastname: Mahr
authors.forename: Mårten
authors.initials: M
authors.lastname: Segelmark
authors.forename: Jan W
authors.initials: JW
authors.lastname: Cohen-Tervaert
authors.forename: David
authors.initials: D
authors.lastname: Scott
mesh_terms: D000465:Algorithms; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015267:Churg-Strauss Syndrome / Q000145:classification; D014890:Granulomatosis with Polyangiitis / Q000145:classification; D006801:Humans; D010488:Polyarteritis Nodosa / Q000145:classification* / Q000453:epidemiology / Q000276:immunology; D014657:Vasculitis / Q000145:classification* / Q000453:epidemiology / Q000276:immunology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers