What are the diagnostic criteria and treatment options for rheumatoid arthritis?

Diagnosing Rheumatoid Arthritis

Use the 2010 ACR/EULAR Classification Criteria, which requires a score of ≥6/10 points based on joint involvement, serology, acute phase reactants, and symptom duration to diagnose rheumatoid arthritis. 1

Target Population for Testing

• Apply diagnostic criteria only to patients with at least one joint showing definite clinical synovitis (swelling) that is not better explained by another disease. 1, 2
• Symmetric involvement of small joints—particularly metacarpophalangeal (MCP) joints, proximal interphalangeal (PIP) joints, wrists, and metatarsophalangeal (MTP) joints—is characteristic of RA. 3
• Large joints (shoulders, elbows, hips, knees, ankles) may also be affected, but distal interphalangeal joints, first carpometacarpal joints, and first MTP joints are typically spared. 3

The 2010 ACR/EULAR Scoring System

A score of ≥6/10 points is required for definite RA classification. 1 Calculate the score by adding points from four categories:

A) Joint Involvement (0-5 points)

• 1 large joint = 0 points 1
• 2-10 large joints = 1 point 1
• 1-3 small joints (with or without large joint involvement) = 2 points 1
• 4-10 small joints (with or without large joint involvement) = 3 points 1

• 10 joints, including at least 1 small joint = 5 points 1

B) Serology (0-3 points)

• Negative RF and negative ACPA = 0 points 1
• Low positive RF or low positive ACPA = 2 points 1
• High positive RF or high positive ACPA = 3 points 1

Critical caveat: Seronegative RA accounts for 20-30% of cases, so negative RF does not exclude RA. 3, 4 Do not delay treatment waiting for positive serology—seronegative RA has a similar prognosis to seropositive disease. 3, 4

C) Acute Phase Reactants (0-1 point)

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

Use CRP rather than ESR because it is more reliable, simpler, and not age-dependent. 1 However, acute phase reactants can be normal even in active disease, so do not dismiss the diagnosis based on normal inflammatory markers. 3

D) Duration of Symptoms (0-1 point)

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

Essential Clinical Examination

Perform a 28-joint count assessment examining for tenderness and swelling in: 1, 3

• PIPs (1st through 5th bilaterally)
• MCPs (1st through 5th bilaterally)
• Wrists
• Elbows
• Shoulders
• Knees

Squeeze test of MCPs and MTPs helps assess for clinical synovitis. 3

Look for early-morning stiffness lasting ≥1 hour and difficulty making a fist. 3, 4

Laboratory Workup

Initial Testing

• ACPA (anti-citrullinated protein antibody): High specificity (90%) with moderate sensitivity (60%) 3
• Rheumatoid factor (RF): Lower specificity (70%) with similar sensitivity to ACPA 3
• CRP (preferred over ESR) 1
• Complete blood count with differential 3, 5
• Comprehensive metabolic panel (liver function, renal function, glucose, urate) 3
• Urinalysis 3

Additional Testing When Diagnosis is Uncertain

• ANA to screen for other connective tissue diseases 3
• HLA-B27 if spondyloarthropathy is being considered 3

Pre-Treatment Screening (Before Biologics)

• Hepatitis B, Hepatitis C, and tuberculosis screening are required before starting any biologic therapy. 3, 5

Imaging Studies

Baseline Imaging

Obtain bilateral hand, wrist, and foot X-rays at baseline to detect erosions and monitor structural damage progression. 3, 4

Conventional radiography findings include: 3

• Periarticular osteopenia
• Uniform joint space narrowing
• Osseous erosions

Erosions predict RA diagnosis and disease persistence. 3

Advanced Imaging (When Criteria Not Met)

• Ultrasound is superior to clinical examination for detecting inflammation and structural damage, and can detect synovitis that predicts disease progression. 3
• Power Doppler ultrasound is useful when patients with early arthritis do not meet the 2010 ACR/EULAR criteria. 3
• MRI with IV contrast is more sensitive than ultrasound in early stages, detecting bone marrow edema (osteitis), which is the best single predictor of future disease progression and functional deterioration. 3

Clinical Examples

Example of early RA diagnosis: A patient with early-morning stiffness, a swollen wrist joint, and strongly positive ACPA test results for 6 weeks (or less with an abnormal CRP) fulfills the criteria for RA, and disease-modifying therapy should be initiated. 1

Differential Diagnoses to Exclude

Before diagnosing RA, exclude: 1, 3, 4

• Psoriatic arthritis
• Gout (check uric acid level)
• Hemochromatosis
• Systemic lupus erythematosus
• Spondyloarthropathies
• Crystal arthropathies
• Polymyalgia rheumatica
• Still's disease

Urgent Referral Strategy

Patients with suspected early RA should be seen within 1-2 weeks of referral through "early arthritis clinics" or urgent appointment slots. 1 Early diagnosis allows for earlier treatment with disease-modifying antirheumatic drugs, which is associated with better outcomes. 2, 5

Disease Activity Assessment After Diagnosis

Once RA is diagnosed, quantitative assessment of disease activity is essential using composite measures: 1, 3

• DAS28 (Disease Activity Score using 28 joint counts) 3
• SDAI (Simplified Disease Activity Index): Remission ≤3.3, low disease activity ≤11 3, 4
• CDAI (Clinical Disease Activity Index): Remission ≤2.8, low disease activity ≤10 3

Include patient-reported outcomes: 1

• Pain assessment
• Patient Global Assessment of Disease Activity
• Health Assessment Questionnaire Disability Index

The primary target of treatment is remission or low disease activity. 3, 6