Credit: Radiographic erosions of metatarsophalangeal joints, especially MTP3. Image courtesy of Susanna M. Proudman.

Overlooking the feet can cause active disease to be missed and treatment efficacy to be overestimated in patients with early rheumatoid arthritis (RA), according to separate reports from Mihir Wechalekar et al. and Marije Bakker and colleagues. In the treat-to-target era, these new findings emphasize the need to adapt disease measures designed for clinical studies for use in individual patients.

“We have been concerned by the increasing use of disease activity and remission criteria that omit joints of the feet,” begins Wechalekar, adding that synovitis of the feet is often the first, and can be the only, manifestation in early RA. To assess the validity of this concern, the group used various tools—including the 28-joint Disease Activity Score (DAS28, which excludes feet) as well as criteria that include full joint counts—to assess disease activity and response to therapy in 123 patients with early RA in a routine clinic setting. Overall, approximately one third of patients deemed to be in remission at 6 months without foot assessment had active disease when feet were considered.

In a different approach, Bakker and colleagues divided a cohort of patients with RA by the stage of their disease and whether it progressed predominantly in hands, feet or both, and statistically analyzed the relationship between radiographic damage scores and DAS28. “DAS28 underestimated disease activity and the expected joint damage, especially during the first 2 years of disease,” summarizes Bakker.

These data, as both authors stress, support the importance of regular assessment of the joints of the feet and ankles in order to reliably estimate disease activity. Especially for patients in whom feet are predominately affected, neglect of these joints might cause a state of remission to be erroneously declared, and the wrong treatment decisions to be made.