Classification of vasculitis.
The sensitivities and specificities of the classification rules of the seven major forms of vasculitis studied varied considerably from 70% to over 99% (Table 2.) High values as found for giant cell (temporal) arteritis, Takayasu arteritis, and Churg-Strauss syndrome, indicate clinically well defined conditions. In contrast, the lowest sensitivity and specificity resulted for the classification of hypersensitivity vasculitis, in which definitions and manifestations are subject to great variation. In a number of instances collection of important clinical data was incomplete. This may have had the effect of reducing sensitivities and specificities to some extent. Because all the cases studied had vasculitis, these criteria are not appropriate to use for diagnosis of individual patients. Development of diagnostic criteria also requires comparison of patients who do not have vasculitis. Development of criteria by two different methods provides some flexibility. Both formats should prove easy to use. Although biopsy is not needed in all patients for classification purposes, histology should be performed as frequently as possible to document the vasculitic nature of the disorder. These criteria sets should be used in the description of patients with vasculitis to enhance uniformity of reporting. As other characteristics of these disorders are identified, more accurate classification rules may be revised.