What assessments are recommended for diagnosing rheumatoid arthritis?

Comprehensive Assessment for Rheumatoid Arthritis Diagnosis

Diagnosis of rheumatoid arthritis requires assessment of definite clinical synovitis in at least one joint not better explained by another disease, along with application of the 2010 ACR/EULAR classification criteria which includes evaluation of joint involvement, serology, acute phase reactants, and symptom duration. 1

Core Diagnostic Criteria

• The 2010 ACR/EULAR Classification Criteria uses a score-based algorithm requiring ≥6/10 points for definite RA diagnosis 1
• Assessment must include at least one joint with definite clinical synovitis (swelling) not better explained by another condition 2, 1
• The scoring system evaluates four domains:
  • Joint involvement (0-5 points): 1 large joint = 0,2-10 large joints = 1-3 small joints = 2,4-10 small joints = 3, >10 joints = 5 1
  • Serology (0-3 points): negative RF and ACPA = 0, low positive RF or ACPA = 2, high positive RF or ACPA = 3 1
  • Acute phase reactants (0-1 points): normal CRP and ESR = 0, abnormal CRP or ESR = 1 1
  • Symptom duration (0-1 points): <6 weeks = 0, ≥6 weeks = 1 1

Clinical Examination

• Focus on symmetric polyarthritis pattern affecting multiple joints, particularly:
  • Metacarpophalangeal joints (MCPs) 3
  • Proximal interphalangeal joints (PIPs) 3
  • Wrists 3
  • Metatarsophalangeal joints 1
• Perform 28-joint count assessment, examining for tenderness and swelling in PIPs, MCPs, wrists, elbows, shoulders, and knees 2, 3
• Assess for morning stiffness lasting ≥60 minutes, which is characteristic of inflammatory arthritis 3
• Note that distal interphalangeal joints, first carpometacarpal joints, and first metatarsophalangeal joints are typically spared in RA 1

Laboratory Assessment

• Anti-citrullinated protein antibody (ACPA) testing - high specificity (90%) with moderate sensitivity (60%) 2, 1
• Rheumatoid factor (RF) testing - lower specificity (70%) with similar sensitivity to ACPA 2, 4
• C-reactive protein (CRP) - preferred over ESR as it's more reliable and not age-dependent 2
• Complete blood count with differential 5
• Renal and hepatic function tests 5
• Screen for hepatitis B, hepatitis C, and tuberculosis before initiating biologic agents 1, 5

Imaging Studies

• Conventional radiography of hands and feet as initial imaging to detect damage 1
• Ultrasound to detect synovitis not evident on clinical examination 2, 1
• MRI for early detection of bone marrow edema and synovitis in cases where diagnosis remains uncertain 1

Disease Activity Assessment

• Use composite measures to determine disease activity:
  • Disease Activity Score using 28 joint counts (DAS28) - recommended by EULAR 2
  • Simplified Disease Activity Index (SDAI) - doesn't require complex calculations 2
  • Clinical Disease Activity Index (CDAI) - doesn't require acute-phase reactant measurement 2
• Include patient-reported outcomes:
  • Pain assessment 2
  • Patient Global Assessment of Disease Activity 2
  • Health Assessment Questionnaire Disability Index 2
• Evaluator global assessment performed by physician, trained nurse, or physician assistant 2

Common Pitfalls to Avoid

• Relying solely on clinical examination may underestimate joint involvement; consider imaging for subclinical inflammation 3
• Overreliance on RF results alone for diagnosis may lead to misdiagnosis or delayed treatment 4
• Early RA may present with only a few affected joints, making diagnosis challenging 3
• Failure to differentiate RA from other inflammatory arthritides by not carefully assessing joint pattern and extra-articular features 3

Clinical Approach Algorithm

1. Identify clinical synovitis in at least one joint not explained by another condition 1
2. Apply the 2010 ACR/EULAR criteria scoring system 1
3. If score ≥6/10, diagnose as definite RA 1
4. If score <6/10, consider advanced imaging (ultrasound or MRI) to detect subclinical synovitis 1
5. Assess disease activity using composite measures to guide treatment decisions 2, 1
6. Refer to rheumatologist promptly, ideally within 6 weeks of symptom onset 4