Fast Five Quiz: Arthritis

Herbert S. Diamond, MD


July 28, 2020

The 2010 ACR/EULAR classification criteria for RA are designed to identify patients with unexplained inflammatory arthritis in at least one peripheral joint and a short duration of symptoms who would benefit from early therapeutic intervention. According to the ACR/EULAR criteria, patients who should be tested are those (1) who have at least one joint with definite clinical synovitis and (2) whose synovitis is not better explained by another disease (eg, lupus, psoriatic arthritis, or gout).

The ACR/EULAR classification system is a score-based algorithm for RA that incorporates the following four 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 or higher. Patients with a score lower than 6 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:

  • One large joint = 0 points

  • Two to 10 large joints = 1 point

  • One to three small joints (with or without involvement of large joints) = 2 points

  • Four to 10 small joints (with or without involvement of large joints) = 3 points

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

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

  • Negative RF and negative ACPA test results = 0 points

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

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

At least one abnormal result on an acute-phase reactant test 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) level and normal erythrocyte sedimentation rate (ESR) = 0 points

  • Abnormal CRP level 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:

  • Less than 6 weeks = 0 points

  • 6 weeks or more = 1 point

Read more about the classification of RA.


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