What point-based diagnostic criteria are used to classify rheumatoid arthritis?

Diagnostic Criteria for Rheumatoid Arthritis

The 2010 ACR/EULAR classification criteria are used to diagnose rheumatoid arthritis, requiring a score of ≥6 out of 10 points across four domains: joint involvement, serology, acute phase reactants, and symptom duration. 1

Target Population for Testing

Before applying the scoring system, two prerequisites must be met:

• At least 1 joint with definite clinical synovitis (swelling) on examination
• The synovitis is not better explained by another disease (e.g., systemic lupus erythematosus, psoriatic arthritis, gout) 1

The Point-Based Scoring System

A) Joint Involvement (0-5 points)

• 1 large joint: 0 points
• 2-10 large joints: 1 point
• 1-3 small joints (with or without large joint involvement): 2 points
• 4-10 small joints (with or without large joint involvement): 3 points
• >10 joints (including at least 1 small joint): 5 points

Large joints include shoulders, elbows, hips, knees, and ankles. Small joints include metacarpophalangeal joints, proximal interphalangeal joints, 2nd-5th metatarsophalangeal joints, thumb interphalangeal joints, and wrists. Note that distal interphalangeal joints, first carpometacarpal joints, and first metatarsophalangeal joints are specifically excluded from assessment. 1

B) Serologic Findings (0-3 points)

At least one test result is required:

• Negative RF and negative ACPA: 0 points
• Low positive RF or low positive ACPA: 2 points
• High positive RF or high positive ACPA: 3 points

Low positive means values >upper limit of normal (ULN) but ≤3× ULN. High positive means values >3× ULN. When RF is only reported as positive/negative, treat positive as low positive. 1

C) Acute Phase Reactants (0-1 point)

At least one test result is required:

• Normal CRP and normal ESR: 0 points
• Abnormal CRP or abnormal ESR: 1 point

Normal/abnormal is determined by local laboratory standards. 1

D) Duration of Symptoms (0-1 point)

Patient self-report of symptom duration:

• <6 weeks: 0 points
• ≥6 weeks: 1 point 1

Interpretation and Clinical Application

A total score of ≥6/10 is required for definite classification as RA. 1 For example, a patient with early-morning stiffness, one swollen wrist joint (2 points), strongly positive ACPA (3 points), and symptoms for 6 weeks (1 point) achieves a score of 6 and fulfills criteria for RA, warranting immediate disease-modifying therapy. 1

Important Caveats

Patients with erosive disease typical of RA with a history compatible with previously fulfilling the 2010 criteria should be classified as having RA, even if they don't currently meet the point threshold (e.g., due to treatment or inactive disease). 1

Patients scoring <6/10 are not classifiable as RA at that time, but their status can be reassessed as criteria might be fulfilled cumulatively over time. 1

Imaging evidence of synovitis (ultrasound or MRI) can confirm joint involvement when clinical examination is equivocal. 1

The 2010 criteria represent a paradigm shift from the 1987 ACR criteria by focusing on early disease features associated with persistent and/or erosive disease rather than late-stage manifestations, enabling earlier diagnosis and treatment initiation to prevent joint destruction. 2 However, be aware that the risk of misclassification is higher than with the 1987 criteria, particularly in RF-positive patients, as RF has only moderate specificity compared to the highly specific ACPA. 3