What is the workup for Rheumatoid Arthritis (RA) and its associated conditions?

Workup for Rheumatoid Arthritis and Associated Conditions

The comprehensive workup for rheumatoid arthritis should include specific laboratory tests (RF, anti-CCP, ESR, CRP), imaging studies (radiographs, ultrasound), and assessment for associated conditions, with ultrasound being particularly valuable when clinical assessment is uncertain. 1

Laboratory Testing

Essential Serological Tests

• Rheumatoid Factor (RF): Sensitivity 69-84%, specificity 78-85% 1
• Anti-citrullinated protein antibodies (ACPA/anti-CCP): Sensitivity 67-78.5%, specificity 95-98% - highest specificity for RA diagnosis 1, 2
• Inflammatory markers:
  • Erythrocyte Sedimentation Rate (ESR)
  • C-Reactive Protein (CRP)
  • Both should be performed at baseline and repeated when clinically relevant 1

Additional Laboratory Tests

• Complete Blood Count (CBC): To assess for anemia of chronic disease 3
• Liver function tests: AST/ALT, alkaline phosphatase, albumin 3
• Renal function: Creatinine 3
• Thyroid Function Tests: As part of diagnostic workup 1
• Hepatitis B/C serology: Particularly important before initiating treatment 3

Imaging Studies

Conventional Radiography

• Plain radiographs of hands and feet (posteroanterior view) should be the initial imaging modality 1
• Early features include soft tissue swelling and juxtaarticular osteoporosis 4
• Should be repeated every 6-12 months during the first years to monitor structural damage 1

Advanced Imaging

• Ultrasound: Superior to clinical examination for detecting joint inflammation 1

  • Particularly valuable when there is doubt about inflammatory activity based on clinical assessment 3
  • Can detect synovitis, erosions, and tenosynovitis 1
  • Power Doppler ultrasound helps predict progression from undifferentiated inflammatory arthritis to RA 1

• Magnetic Resonance Imaging (MRI):

  • More sensitive than radiographs for detecting early erosions and synovitis 1
  • Can detect bone edema which predicts progression to RA 1
  • Flexor tenosynovitis is a predictor of early RA 1

Disease Activity Assessment

Regular monitoring of disease activity is essential using validated composite measures:

• Disease Activity Score (DAS28) 3, 1
• Simplified Disease Activity Index (SDAI) 3, 1
• Clinical Disease Activity Index (CDAI) 3, 1
• Patient Activity Scale (PAS) or PAS-II 3
• Routine Assessment of Patient Index Data 3 (RAPID-3) 3

These measures should be used every 1-3 months until remission is achieved 1.

Differential Diagnosis Considerations

The workup must rule out conditions that can mimic RA 3, 1:

• Crystal arthropathies (gout, pseudogout)
• Psoriatic arthritis
• Spondyloarthritis
• Systemic lupus erythematosus
• Osteoarthritis
• Fibromyalgia
• Polymyalgia rheumatica
• Still's disease
• Idiopathic inflammatory myopathies
• Vasculitis
• Reactive arthritis
• Paraneoplastic syndromes

Assessment of Associated Conditions

Cardiovascular Assessment

• Cardiovascular risk assessment is essential as RA is associated with 50% increase in cardiovascular morbidity and mortality 3
• Lipid profile testing is recommended 3
• Assessment for traditional cardiovascular risk factors (hypertension, diabetes, smoking) 3

Pulmonary Evaluation

• Chest radiograph: Baseline assessment 3
• Consider pulmonary function tests and high-resolution CT for patients with respiratory symptoms 5
• Up to half of RA patients exhibit extra-articular manifestations, with pulmonary involvement being a significant contributor to morbidity and mortality 5

Other Associated Conditions

• Screen for depression and other psychosocial factors 3
• Assess for chronic kidney disease 3
• Check for hypothyroidism 3
• Consider evaluation for periodontitis 3
• Vitamin D levels may be relevant 3

Diagnostic Criteria

The 2010 ACR/EULAR Classification Criteria should be applied, with a score of ≥6/10 indicating definite RA diagnosis 1:

• Joint involvement (0-5 points)
• Serology: RF and anti-CCP (0-3 points)
• Acute phase reactants: ESR and CRP (0-1 point)
• Duration of symptoms (0-1 point)

Common Pitfalls to Avoid

1. Relying solely on laboratory tests: More than 30% of RA patients have negative RF or anti-CCP, and 40% have normal ESR or CRP 6

2. Missing comorbid conditions: Conditions like obesity and fibromyalgia may complicate assessment of disease activity 3, 1

3. Delayed diagnosis: Early diagnosis and treatment can avert or substantially slow progression of joint damage in up to 90% of patients 7

4. Inadequate monitoring: Disease activity should be monitored every 1-3 months until remission, with treatment adjusted accordingly 3, 1

5. Overlooking extra-articular manifestations: These can significantly contribute to morbidity and mortality 5

By following this comprehensive approach to RA workup, clinicians can ensure accurate diagnosis, appropriate treatment initiation, and effective monitoring of disease progression and associated conditions.