Introduction The new American College for Rheumatology (ACR)/European League Against Rheumatism (EULAR) remission criteria are based on the assessment of 28 joints. A study was undertaken to study the consequences of remission misclassification due to residual disease activity in the feet on physical function and joint damage in the subsequent year in an observational early disease cohort.

Methods All patients with rheumatoid arthritis at inclusion or at 1-year follow-up in the early arthritis cohort of the Jan van Breemen Institute, The Netherlands were included. ACR/EULAR remission definitions for trials and clinical practice were calculated twice, once using a 28-joint count and once using a 38-joint count that included the 10 metatarsophalangeal joints. Disease stability was defined as stable x-ray scores over 1 year (change ≤0 in Sharp/van der Heijde scores) and stable and low scores on the Health Assessment Questionnaire (HAQ change ≤0 and HAQ score consistently ≤0.5), all during the second year after inclusion. Analyses comprised residual disease activity (swollen or tender joints >0) in the feet of patients who fulfilled the candidate remission criteria using a 28-joint count and likelihood ratios of remission definitions to predict disease stability.

Results Of 421 patients, 9–15% reached remission at 1 year using a 28-joint count. Of these, 26–40% showed activity in the feet. Misclassification due to reduced joint counts was observed in 2–3%. A state of remission increased the likelihood of stability of both x-ray and HAQ, with similar likelihood ratios for definitions using 38-joint counts and those using 28-joint counts.

Conclusion The ability of remission definitions with 28-joint counts versus 38-joint counts to predict long-term good radiological and functional outcome is similar. This confirms that inclusion of ankles and forefeet in the assessment of remission is not required, although inclusion of these joints in the examination is recommended.