What is the presentation and workup for rheumatoid arthritis (RA)?

Presentation and Workup of Rheumatoid Arthritis

Rheumatoid arthritis typically presents as symmetric polyarthritis with joint swelling, especially of the hands and feet, accompanied by morning stiffness lasting at least 1 hour, and requires a comprehensive laboratory and clinical assessment for accurate diagnosis. 1

Clinical Presentation

Cardinal Features

• Symmetric polyarthritis affecting:
  • Metacarpophalangeal joints
  • Proximal interphalangeal joints
  • Wrists
  • Metatarsophalangeal joints
  • Knees 1, 2
• Morning stiffness lasting ≥1 hour (key distinguishing feature) 2
• Joint swelling and tenderness on palpation with motion impairment 2

Systemic Symptoms

• Fatigue
• Low-grade fever
• Weight loss
• Malaise 1, 2

Patterns of Onset

• Insidious onset (most common): Gradual development of pain with symmetric small joint swelling
• Acute/subacute onset (25% of patients)
• Palindromic onset: Recurrent episodes of oligoarthritis without residual damage
• Monoarticular presentation
• Extra-articular synovitis: Tenosynovitis, bursitis
• Polymyalgic-like onset: Can mimic polymyalgia rheumatica in elderly 2

Extra-articular Manifestations

• Rheumatoid nodules (marker of severe disease)
• Inflammatory eye disease
• Interstitial lung disease
• Vasculitis
• Hematologic abnormalities
• Felty's syndrome 1, 2, 3

Diagnostic Workup

Laboratory Assessment

1. Essential blood tests:

   • Erythrocyte sedimentation rate (ESR)
   • C-reactive protein (CRP)
   • Rheumatoid factor (RF)
   • Anti-citrullinated protein/peptide antibodies (anti-CCP)
   • Complete blood count
   • Basic biochemistry 1

2. Key serological markers:

   Test	Sensitivity	Specificity	Comments
   Anti-CCP	67-78.5%	95-98%	Highest specificity, included in 2010 ACR/EULAR criteria
   RF	69-84%	78-85%	Higher sensitivity but lower specificity

   Important caveat: More than 30% of RA patients may have negative tests for RF or anti-CCP antibodies, and 40% may have normal ESR or CRP 4

Disease Activity Assessment

• Composite measures recommended for diagnosis and monitoring:
  • Disease Activity Score using 28 joint counts (DAS28)
  • Simplified Disease Activity Index (SDAI)
  • Clinical Disease Activity Index (CDAI) 5, 1
  • Patient Activity Scale (PAS)
  • Patient Activity Scale-II (PAS-II)
  • Routine Assessment of Patient Index Data 3 (RAPID-3) 5

Imaging Studies

1. Plain radiographs of hands and feet:

   • Early findings: Soft tissue swelling and juxtaarticular osteoporosis
   • Should be performed every 6-12 months during first few years 5, 2

2. Ultrasonography:

   • Detects synovial thickening even in finger joints
   • Useful for early assessment and follow-up 2

3. Additional imaging when indicated:

   • Magnetic resonance imaging (MRI)
   • Computed tomography (CT) 2

Diagnostic Algorithm

1. Initial assessment:

   • Document pattern of joint involvement (symmetric polyarthritis)
   • Assess duration of morning stiffness (≥1 hour suggests inflammatory arthritis)
   • Evaluate for systemic symptoms

2. Laboratory testing:

   • Order RF, anti-CCP, ESR, CRP, CBC, and basic biochemistry
   • Remember that negative serologies do not exclude diagnosis

3. Disease activity measurement:

   • Calculate DAS28 or another validated composite measure
   • DAS28 score ≥6/10 indicates definite RA diagnosis 1

4. Radiographic assessment:

   • Obtain baseline radiographs of hands and feet
   • Look for early erosive changes

5. Differential diagnosis considerations:

   • Psoriatic arthritis
   • Gout
   • Hemochromatosis 1

Common Pitfalls to Avoid

1. Delayed referral to rheumatologist (should occur within 6 weeks of symptom onset) 1

2. Overreliance on laboratory tests - remember that >30% of RA patients may have negative RF or anti-CCP, and 40% may have normal inflammatory markers 4

3. Confusing fibromyalgia with active RA - patients with fibromyalgia can have falsely elevated disease activity scores due to high tender joint counts 1

4. Missing extra-articular manifestations that may indicate more severe disease 1, 3

5. Inadequate monitoring - disease activity should be assessed at 1-3 month intervals until remission is achieved 5

Prognostic Considerations

• Life expectancy is shortened by 3-5 years in RA patients, especially those with extra-articular disease 1
• Work disability begins early, with only 80% of patients working at 2 years and 68% at 5 years 1
• Poor prognostic factors include:
  • Presence of RF or anti-CCP antibodies
  • Early joint damage
  • High disease activity 1, 6

Early diagnosis and prompt initiation of disease-modifying therapy are essential for improving outcomes and reducing joint damage in patients with rheumatoid arthritis 1, 6.