What is the recommended approach to diagnose and treat temporal arteritis?

Diagnosing Temporal Arteritis (Giant Cell Arteritis)

Temporal artery biopsy remains the gold standard diagnostic test for giant cell arteritis (GCA) in the United States, with a long-segment specimen (>1 cm) preferred to increase diagnostic yield. 1

Clinical Presentation and Initial Evaluation

Key Clinical Features to Assess

• Age: Patients ≥50 years (strong predictor with positive likelihood ratio of 4.1) 2, 1
• Headache: New-onset or change in headache pattern, often in temporal area 1
• Temporal artery abnormalities: Tenderness, thickening, or decreased pulsation 1
• Visual symptoms: Amaurosis fugax, diplopia, vision loss (ophthalmological emergency) 3
• Jaw claudication: Highly specific symptom (positive likelihood ratio of 4.2) 2, 1
• Constitutional symptoms: Fever, fatigue, weight loss 1
• Scalp tenderness: When combing hair or lying on pillow 1

Laboratory Tests

• Erythrocyte Sedimentation Rate (ESR): Typically elevated >50 mm/hr 1
  • ESR >100 mm/hr has positive likelihood ratio of 3.1 2
• C-Reactive Protein (CRP): Elevated levels support diagnosis 2
• Platelet count: Elevation >400 × 10³/μL has positive likelihood ratio of 3.8 1

Diagnostic Algorithm

1. Initial Assessment:

   • Complete clinical evaluation for symptoms and signs listed above
   • Order ESR, CRP, and complete blood count

2. Diagnostic Testing:

   • Temporal Artery Biopsy (TAB): Recommended within 2 weeks of starting glucocorticoid therapy 1

     • Long-segment specimen (>1 cm) preferred
     • Unilateral biopsy is usually sufficient, but bilateral may increase yield
     • Remains diagnostic standard in the US 2

   • Temporal Artery Ultrasound:

     • Conditionally recommended in centers with appropriate expertise 1
     • Look for "halo sign" (dark halo around arterial lumen) 4
     • 81% sensitivity and 88% specificity; bilateral halo sign has 100% specificity 4
     • May be particularly useful in emergency settings 1

   • Large Vessel Imaging:

     • Recommended in newly diagnosed cases to evaluate extent of disease 1
     • Options include MRI, CT angiography, or PET-CT

Important Diagnostic Considerations

• Do not delay treatment while awaiting biopsy results if clinical suspicion is high, especially with visual symptoms 1, 3
• Negative biopsy does not rule out GCA due to skip lesions; clinical judgment remains important 5
• No single symptom, physical sign, or laboratory test is sufficient to completely rule in or rule out GCA 2
• Diagnostic pitfalls:
  • GCA can mimic other conditions including angle-closure glaucoma, migraine, trigeminal neuralgia, and carotid artery disease 5
  • Headache and scalp tenderness alone are poorly informative in patients with suspected GCA 2
  • Relying solely on ESR can be misleading as it may be normal in some cases

Treatment Initiation

• Immediate high-dose glucocorticoid therapy is essential when GCA is strongly suspected 1, 6
  • Prednisone 40-60 mg/day orally for typical cases 1
  • Methylprednisolone 500-1000 mg/day intravenously for patients with visual symptoms 1, 6
  • Treatment should not be delayed while awaiting biopsy results 1

Follow-up and Monitoring

• Regular clinical assessment for symptom improvement
• Serial ESR and CRP measurements to monitor disease activity
• Follow-up imaging may be useful to assess large vessel involvement
• Ultrasound monitoring: Halo sign typically disappears within 2-4 weeks (mean 21 days) after starting treatment 4

By following this diagnostic approach, clinicians can promptly identify and treat temporal arteritis, potentially preventing the devastating complication of permanent vision loss.