What is the 2010 ACR/EULAR classification system for rheumatoid arthritis (RA)?

Updated: Mar 05, 2021
  • Author: Howard R Smith, MD; Chief Editor: Herbert S Diamond, MD  more...
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The ACR/EULAR classification system is a score-based algorithm for RA that incorporates the following 4 factors:

  • Joint involvement

  • Serology test results

  • Acute-phase reactant test results

  • Patient self-reporting of the duration of signs and symptoms

The maximum number of points possible is 10. A classification of definitive RA requires a score of 6/10 or higher. Patients with a score lower than 6/10 should be reassessed over time. If patients already have erosive changes characteristic of RA, they meet the definition of RA, and application of this diagnostic algorithm is unnecessary.

Joint involvement consists of swelling or tenderness upon examination. The presence of synovitis may be confirmed on imaging studies. Points are allocated as follows:

  • 1 large joint (ie, shoulders, elbows, hips, knees, ankles) = 0 points

  • 2-10 large joints = 1 point

  • 1-3 small joints (with or without involvement of large joints), such as MCP, PIP, second to fifth MTP, thumb interphalangeal (IP), and wrist joints = 2 points

  • 4-10 small joints (with or without involvement of large joints) = 3 points

  • More than 10 joints (at least 1 small joint, plus any combination of large and additional small joints or joints such as the temporomandibular, acromioclavicular, or sternoclavicular) = 5 points

At least 1 serology test result is needed for RA classification. Points are allocated as follows:

  • Negative rheumatoid factor (RF) and negative anti−citrullinated protein antibody (ACPA; in the ACR/EULAR criteria set, tested as anti−cyclic citrullinated peptide [anti-CCP]) = 0 points

  • Low-positive RF or low-positive ACPA = 2 points

  • High-positive RF or high-positive ACPA = 3 points

Negative serology test results are defined as international unit (IU) values that do not exceed the upper limit of normal (ULN) for the reporting laboratory or assay. Low-positive results are defined as IU values that exceed the ULN but are no more than 3 times the ULN for the reporting laboratory or assay. High-positive results are IU values that are more than 3 times higher than the ULN for the reporting laboratory or assay. When RF is available only as a positive or negative finding, a positive result should be scored as low-positive RF.

At least 1 test acute-phase reactant test result is needed for classification. Local laboratory standards determine which results are normal and which are abnormal. Points are allocated as follows:

  • Normal C-reactive protein (CRP) and normal erythrocyte sedimentation rate (ESR) = 0 points

  • Abnormal CRP or abnormal ESR = 1 point

Points for the patient’s self-reporting of the duration of signs or symptoms of synovitis in clinically involved joints are allocated as follows:

  • Shorter than 6 weeks = 0 points

  • 6 weeks or longer = 1 point

A 2014 systematic literature review by Radner et al concluded that the 2010 ACR/EULAR criteria have a pooled sensitivity for RA of 0.82 (95% confidence index [CI], 0.79-0.84) and a specificity of 0.61 (95% CI, 0.59-0.64). These authors' review of research that directly compared the 2010 ACR/EULAR criteria with 1987 ACR criteria found that the ACR/EULAR criteria had higher overall sensitivity (+0.11 compared with 1987 criteria) at the cost of lower overall specificity (-0.04). [40]

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