ACR/EULAR RA Criteria Calculator
2010 ACR/EULAR Classification Criteria for Rheumatoid Arthritis
Classification Criteria
Prerequisites: At least 1 joint with definite clinical synovitis AND synovitis not better explained by another disease.
Large joints: shoulders, elbows, hips, knees, ankles
Small joints: MCPs, PIPs, 2nd-5th MTPs, thumb IPs, wrists
Low-positive: > ULN but ≤ 3× ULN
High-positive: > 3× upper limit of normal (ULN)
Classification Result
Score Breakdown
Classification Threshold
Score ≥ 6 out of 10: Definite Rheumatoid Arthritis
These are classification criteria for research, not diagnostic criteria. Clinical judgment remains essential.
First-Line Treatment
- • Methotrexate: Gold standard DMARD
- • Target: Remission or low disease activity
- • Timing: Start within 3 months of symptom onset
- • Add: Folic acid, consider hydroxychloroquine
⚠️ Important
Exclude other causes: psoriatic arthritis, SLE, viral arthritis, crystalline arthropathy, etc.
Understanding ACR/EULAR RA Criteria
The 2010 American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) classification criteria for rheumatoid arthritis replaced the 1987 ACR criteria. These new criteria were designed to identify early RA, allowing for earlier intervention and better outcomes.
Key Changes from 1987 Criteria
- Focus on early disease identification (can classify RA before erosions develop)
- Includes anti-CCP (ACPA) antibodies, which weren't available in 1987
- Weighted scoring system rather than checklist
- Emphasizes small joint involvement
- Requires only 6 weeks duration (vs. 6 months in some older criteria)
Prerequisites for Using These Criteria
Before applying the scoring system, two prerequisites must be met:
- At least 1 joint with definite clinical synovitis: Swelling on examination not due to bone proliferation alone
- Synovitis not better explained by another disease: Must exclude SLE, psoriatic arthritis, gout, etc.
Understanding the Four Domains
A. Joint Involvement (0-5 points)
Scores based on number and size of involved joints:
- Large joints: shoulders, elbows, hips, knees, ankles
- Small joints: MCPs, PIPs, 2nd-5th MTPs, thumb IPs, wrists
- DIP joints, 1st CMC, and 1st MTP are excluded (more typical of osteoarthritis)
- Higher scores for small joint and polyarticular involvement
B. Serology (0-3 points)
Tests for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA/anti-CCP):
- Both negative = 0 points
- Low positive (1-3× ULN) of either = 2 points
- High positive (>3× ULN) of either = 3 points
- ACPA more specific than RF for RA
C. Acute Phase Reactants (0-1 point)
Elevated ESR or CRP indicates inflammation. While not specific for RA, helps confirm active inflammatory process.
D. Duration of Symptoms (0-1 point)
Symptoms ≥6 weeks help distinguish RA from self-limited viral arthritis or reactive arthritis.
Clinical Application and Limitations
Important considerations:
- Classification vs. Diagnosis: These are classification criteria for research cohorts, not strict diagnostic criteria
- Clinical Judgment: Experienced clinicians may diagnose RA even if criteria not met
- Exclusions: Must rule out other arthritides first
- Early Disease: Some patients develop RA over time and may not initially meet criteria
- Treatment Threshold: Many rheumatologists treat based on clinical suspicion before criteria are met
Detailed Scoring System
| Domain | Criteria | Points |
|---|---|---|
| Joint Involvement | 1 large joint | 0 |
| 2-10 large joints | 1 | |
| 1-3 small joints (± large joints) | 2 | |
| 4-10 small joints (± large joints) | 3 | |
| >10 joints (≥1 small joint) | 5 | |
| Serology | Negative RF and negative ACPA | 0 |
| Low-positive RF or ACPA (≤3× ULN) | 2 | |
| High-positive RF or ACPA (>3× ULN) | 3 | |
| Acute Phase | Normal CRP and ESR | 0 |
| Abnormal CRP or ESR | 1 | |
| Duration | <6 weeks | 0 |
| ≥6 weeks | 1 |
Total Score ≥ 6/10 = Definite Rheumatoid Arthritis
Frequently Asked Questions
Are these criteria for diagnosis or classification?
These are classification criteria, designed to create homogeneous groups for research studies, not strict diagnostic criteria for individual patients. In clinical practice, rheumatologists may diagnose and treat RA even when criteria aren't fully met, especially in early disease. The criteria help ensure consistency in research but shouldn't replace clinical judgment.
What is the difference between RF and ACPA (anti-CCP)?
Both are autoantibodies found in RA. Rheumatoid factor (RF) is less specific and can be positive in other conditions and healthy individuals (especially elderly). Anti-CCP (ACPA) is highly specific for RA (95%+ specificity) and may appear earlier in disease. Both predict more aggressive disease and erosions. Approximately 70% of RA patients are seropositive for RF or ACPA.
Can I have RA if I'm seronegative (RF and ACPA negative)?
Yes, about 20-30% of RA patients are seronegative. These patients can still develop erosive disease and disability, though typically have a somewhat better prognosis than seropositive patients. Seronegative RA requires more clinical joints (4-10 small joints = 3 points) or polyarticular involvement (>10 joints = 5 points) to reach the threshold of 6 points.
Why are DIP joints excluded from the criteria?
DIP (distal interphalangeal) joint involvement is more characteristic of osteoarthritis and psoriatic arthritis than RA. RA typically affects MCPs (metacarpophalangeal) and PIPs (proximal interphalangeal) joints in a symmetric pattern. The criteria focus on joint patterns more typical of RA to improve specificity.
When should treatment be started?
Current guidelines recommend starting disease-modifying antirheumatic drugs (DMARDs) within 3 months of symptom onset, and ideally even sooner. Early treatment significantly improves long-term outcomes, prevents joint damage, and increases the likelihood of achieving remission. Many rheumatologists treat patients with clinical RA even before they meet formal classification criteria, especially if seropositive.
What is the first-line treatment for RA?
Methotrexate is the gold standard first-line DMARD for RA, typically started at 10-15 mg weekly and increased to 20-25 mg as tolerated. Always give with folic acid to reduce side effects. If methotrexate alone is insufficient after 3 months, add hydroxychloroquine or sulfasalazine (triple therapy), or escalate to biologic DMARDs (TNF inhibitors, JAK inhibitors, etc.). Corticosteroids may be used short-term as a bridge.
How does undifferentiated arthritis relate to these criteria?
Patients with inflammatory arthritis who don't meet criteria for RA or any other specific diagnosis have "undifferentiated arthritis." Some will evolve to definite RA over time, some will develop other defined conditions, and some will remain undifferentiated or achieve remission. Close follow-up is essential as treatment may be warranted even without definite classification.
What other conditions must be excluded before applying these criteria?
Differential diagnosis includes: systemic lupus erythematosus (check ANA, anti-dsDNA), psoriatic arthritis (look for psoriasis, nail changes, DIP involvement), reactive arthritis (recent infection, asymmetric), viral arthritis (parvovirus, hepatitis), crystalline arthropathy (gout, pseudogout - aspirate if mono/oligoarticular), and sarcoidosis. The criteria specify that synovitis must not be "better explained by another disease."