Latest Rheumatoid Arthritis Diagnostic Criteria
The 2010 ACR/EULAR Classification Criteria
The current standard for diagnosing rheumatoid arthritis is the 2010 ACR/EULAR Classification Criteria, which requires a score of ≥6 out of 10 points across four domains: joint involvement, serology, acute phase reactants, and symptom duration. 1, 2
Entry Criterion (Must Be Met First)
- At least one joint must demonstrate definite clinical synovitis (swelling) that is not better explained by another disease 1, 2
- Distal interphalangeal joints, first carpometacarpal joints, and first metatarsophalangeal joints are excluded from assessment 3, 1
Scoring System (Total Score ≥6/10 = Definite RA)
Joint Involvement (0-5 points):
- 1 large joint = 0 points 1, 4
- 2-10 large joints = 1 point 1, 4
- 1-3 small joints (with or without large joints) = 2 points 1
- 4-10 small joints (with or without large joints) = 3 points 1
10 joints (at least one small joint) = 5 points 1
Large joints include shoulders, elbows, hips, knees, and ankles. Small joints include metacarpophalangeal joints, proximal interphalangeal joints, second through fifth metatarsophalangeal joints, thumb interphalangeal joints, and wrists 3, 1.
Serology (0-3 points):
- Negative RF and negative ACPA = 0 points 1
- Low positive RF or low positive ACPA (≤3 times upper limit of normal) = 2 points 1
- High positive RF or high positive ACPA (>3 times upper limit of normal) = 3 points 1
Anti-citrullinated protein antibody (ACPA) testing has high specificity (90%) with moderate sensitivity (60%), while rheumatoid factor has lower specificity (70%) with similar sensitivity 1.
Acute Phase Reactants (0-1 point):
C-reactive protein is preferred over ESR as it is more reliable and not age-dependent 1.
Duration of Symptoms (0-1 point):
Duration refers to patient self-report of signs or symptoms of synovitis (pain, swelling, tenderness) in joints that are clinically involved at assessment, regardless of treatment status 3.
Critical Clinical Pearls
Do not delay diagnosis or treatment waiting for positive serology. Seronegative RA accounts for 20-30% of cases and has similar prognosis to seropositive disease 1, 5. The 2010 criteria assign only 1 point for abnormal inflammatory markers while joint involvement can contribute up to 5 points, emphasizing that clinical synovitis is more important than laboratory values 1.
Do not dismiss RA based on normal ESR/CRP. Acute phase reactants are poor predictors and can be normal even in active disease 1, 5. Experienced clinicians recognize that patients with genuine inflammatory arthritis can have normal acute phase reactants 1.
Patients with erosive disease typical of RA with compatible history should be classified as having RA even without meeting the full scoring criteria. Similarly, patients with long-standing disease who previously fulfilled the criteria should be classified as having RA 4.
Validation and Performance
The 2010 ACR/EULAR criteria demonstrated sensitivity of 92% and specificity of 89% when including clinical and imaging domains, or 85% sensitivity and 78% specificity when excluding imaging 3. These criteria have been extensively validated and show excellent agreement with rheumatologist diagnosis of RA after 2 years of follow-up 6.
The criteria were developed specifically to identify patients at early stages who are at high risk for persistent and/or erosive disease, shifting focus from late-stage features to earlier diagnosis and institution of effective disease-suppressing therapy 2, 7.