Measurement of proximal interphalangeal joint circumference in rheumatoid arthritis: one joint or ten?

Serial measurements of proximal interphalangeal joint circumference using a single joint that was selected as being 'worst' on clinical grounds or the largest joint at baseline were compared with the mean of all 10 joints in patients with active rheumatoid arthritis receiving second-line drugs. Use of the worst joint gave comparable results to the mean of 10 joint measurements, while the largest joint showed earlier and greater improvement than occurred with the mean of 10 joint sizes. Measurement of a single joint saves time without loss of accuracy or sensitivity.