A COMPARISON OF 2 NOMENCLATURE SYSTEMS FOR PRIMARY SYSTEMIC VASCULITIS

Recently, two new systems have been proposed for the nomenclature of p rimary vasculitides: the 1990 American College of Rheumatology (ACR) c lassification criteria and the 1992 Chapel Hill Consensus Conference ( CHCC) definitions. We compared these two systems in the same cohort of patients with primary systemic vasculitis. Twenty-four patients were studied and, applying the 1990 ACR criteria, the diagnoses were Wegene r's granulomatosis (WG) (15), Churg-Strauss syndrome (CSS) (4), polyar teritis nodosa (PAN) (2) and unclassified (3). Using the CHCC definiti ons, the diagnoses were WG (5), microscopic polyangiitis (MPA) (8), po ssible MPA (1), PAN (1) and undefined (9). There was concordance in on ly five patients (all WG). Significant discordance exists between thes e two criteria sets. Since the ACR criteria set does not include MPA, WG tends to be overdiagnosed. The Chapel Hill definitions are biopsy d ependent and surrogate features for the defining histology are require d to allow their practical application.