Objectives The new 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria for rheumatoid arthritis (RA) have been designed to classify early onset RA, but has not been studied to identify RA in patients with arthritis seen in routine clinical care where correct ‘classification’ of patients, when they are not selected for having RA would be important.

Design Prospective, consecutive patients cohort.

Setting Outpatient clinic of a university rheumatology centre.

Participants A total of 126 patients with joint symptoms were consecutively recruited.

Interventions The ACR/EULAR RA criteria were applied, with questions followed by a targeted musculoskeletal exam. The gold standard for the diagnosis of RA was the primary rheumatologist's diagnosis.

Primary outcome measure Number of patients with non-RA diagnosis who were classified as having RA by the new classification criteria.

Results The sensitivity and specificity of the 2010 criteria in classifying RA were 97% and 55%, respectively, compared with the 1987 RA criteria which were 93% and 76%, respectively. The 2010 criteria as applied to this group of patients had a poorer positive predictive (44% vs 61%) and a similar negative predictive value (98% vs 97%) compared with the 1987 criteria. More specifically, 66.7% of systemic lupus erythematosus patients, 50% of osteoarthritis, 37.5% of psoriatic arthritis and 27.2% of others fulfilled the new criteria and could have been classified as RA.

Conclusions In this, we believe, the first study to examine the new 2010 ACR/EULAR RA criteria among consecutive patients seen in routine care, we found the criteria to have low specificity, and therefore incorrectly label those as having RA when, in fact, they may have a different type of inflammatory arthritis. Physicians need to be aware of this when applying the new criteria for classifying their patients for any purpose.