The revised criteria for the classification of rheumatoid arthritis (RA) were formulated from a computerized analysis of 262 contemporary, consecutively studied patients with RA and 262 control subjects with From the Rheumatoid Arthritis Criteria Subcommittee of the Diagnostic and Therapeutic Criteria Committee of the American Rheumatism Association.

Conclusion. Estimates for many specific rheumatic conditions rely on a few, small studies of uncertain generalizability to the US population. This report provides the best available prevalence estimates for the US, but for most specific conditions more studies generalizable to the US or addressing understudied populations are needed. METHODSThe purpose of this study, definitions of general terminology, and methods used for ascertaining the data and

Given the limitations of the data on which they are based, this report provides the best available prevalence estimates for arthritis and other rheumatic conditions overall, and for selected musculoskeletal disorders, in the US population.

Criteria for the classification of Takayasu arteritis were developed by comparing 63 patients who had this disease with 744 control patients with other forms of vasculitis. Six criteria were selected for the traditional format elass$cation: onset at age 1 4 0 years, claudication of an extremity, decreased brachial artery pulse, >10 mm Hg difference in systolic blood pressure between arms, a bruit over the subclavian arteries or the aorta, and arteriographic evidence of narrowing or occlusion of the entire aorta, its primary branches, or large arteries in the proximal upper or lower extremities. The presence of 3 or more of these 6 criteria demonstrated a sensitivity of 90.5% and a specificity of 97.8%. A classification tree also was constructed with 5 of these 6 criteria, omitting claudication of an extremity. The classification tree demonstrated a sensitivity of 92.1% and a specificity of 97.0%.