Detection of small joint synovitis by ultrasonography: the learning curve of rheumatologists

Background: Ultrasonography allows assessment of soft tissue structures and has become a valued tool for diagnosing synovitis. Objective: To assess the learning curve for ultrasonography in evaluating synovitis of the small joints in rheumatoid arthritis. Methods: Metacarpophalangeal (MCP), metatarsophalangeal (MTP), and proximal interphalangeal ( PIP) joints were evaluated using ultrasonography (Esaote AU 5 Epi, linear probe 10 - 13 MHz) by four rheumatologists, the first being experienced ( senior), the others having no ( fellows 1 and 2) or little ( fellow 3) experience in ultrasonography. For each fellow, the learning curve was divided into blocks. In each block the fellow examined five consecutive patients with the senior; then, blinded to the senior's results, two further patients alone ( seven patients examined per block). For each evaluation, the MCP, PIP, and MTP joints were individually tagged as having synovitis or not. The ultrasonography results were compared between fellow and senior for the two last patients of each block, using proportions of agreement and kappa statistics. Results: 70 patients were evaluated ( seven practice patients, followed by nine blocks). For fellows 1 and 2, the proportions of agreement were respectively 42% and 47% (kappa = 0 and 0) at the first evaluation, and rose progressively to 82% and 82% (kappa = 0.63 and 0.62) at the ninth evaluation. For fellow 3, initially good results were followed by decreased accuracy. Conclusions: Detecting synovitis of the MCP, PIP, and MTP joints using ultrasonography can be done accurately by rheumatologists initially not experienced in this technique. At least 70 examinations were necessary to develop competence.