Diagnostic classification of antineutrophil cytoplasmic autoantibody-associated vasculitides.

Antineutrophil cytoplasmic autoantibodies (ANCA) are in the circulation of patients with a variety of clinically and pathologically distinctive forms of necrotizing vasculitis. Some patients have classic manifestations of well-recognized clinicopathologic syndromes, such as Wegener's granulomatosis, microscopic polyarteritis nodosa, and Churg-Strauss syndrome, but many patients are difficult to assign to a diagnostic category. The Ad Hoc Nomenclature Committee of The Third International Workshop on ANCA is attempting to identify a working classification system for ANCA-associated vasculitides. This system takes into account the many shared clinical and pathologic features, and relies on prerequisite positive and negative findings for diagnostic categorization.