What tests are necessary to diagnose and manage giant cell (temporal) arteritis?

Diagnostic Tests for Giant Cell (Temporal) Arteritis

For patients with suspected giant cell arteritis (GCA), a temporal artery biopsy is the recommended diagnostic test, which should be performed within 2 weeks of starting glucocorticoid therapy. 1, 2

Initial Diagnostic Approach

Clinical Assessment

• Age ≥50 years at disease onset
• New-onset or change in headache pattern, often in temporal area
• Temporal artery abnormalities (thickening, tenderness, pulselessness)
• Scalp tenderness
• Jaw claudication
• Visual disturbances (amaurosis fugax, diplopia)
• Less common: respiratory symptoms like chronic nonproductive cough 2

Laboratory Tests

• Erythrocyte sedimentation rate (ESR) - typically elevated >50 mm/hr
• C-reactive protein (CRP) - elevated
• Complete blood count - may show thrombocytosis (platelet count >400 × 10³/μL) 2

Definitive Diagnostic Tests

Temporal Artery Biopsy (First-Line)

• Gold standard for diagnosis 3
• Recommendations:
  • Unilateral biopsy is conditionally recommended over bilateral biopsies
  • Long-segment specimen (>1 cm) is preferred over short-segment (<1 cm)
  • Should be performed within 2 weeks of starting glucocorticoid therapy 1
  • Delay beyond 7 days of steroid treatment may significantly reduce positivity rates 4

Imaging Studies (When Biopsy is Negative or Not Feasible)

• Temporal artery ultrasound
  • Conditionally recommended in centers with appropriate expertise
  • Can be useful in emergency settings to expedite diagnosis 5
  • Less established in US compared to Europe 1
• Other noninvasive vascular imaging options:
  • MRI/MRA of cranial arteries
  • CT angiography
  • FDG-PET/CT 2

Diagnostic Algorithm

1. Suspect GCA based on clinical features and elevated inflammatory markers
2. Initiate glucocorticoid therapy immediately if high clinical suspicion, especially with visual symptoms
   • Prednisone 40-60 mg/day orally for typical GCA
   • Consider IV methylprednisolone 500-1000 mg/day for threatened vision loss 2
3. Arrange temporal artery biopsy within 2 weeks of starting steroids (preferably within 7 days)
4. If biopsy is negative but clinical suspicion remains high:
   • Obtain noninvasive vascular imaging to evaluate large vessel involvement
   • Consider temporal artery ultrasound if available with experienced operators 1, 2
5. Evaluate for large vessel involvement with appropriate imaging in newly diagnosed cases 1

Important Considerations

• Don't delay treatment while awaiting diagnostic confirmation when clinical suspicion is high
• Biopsy timing is critical - sensitivity decreases with prolonged steroid treatment 4
• Confirm diagnosis before committing to long-term therapy - treatment may be needed for years (mean duration ~6 years in some studies) 6
• Consider referral to specialists (rheumatology, ophthalmology) for further management, especially with visual symptoms 2

Common Pitfalls to Avoid

• Delaying glucocorticoid treatment when GCA is strongly suspected, particularly with visual symptoms
• Waiting too long after steroid initiation to perform temporal artery biopsy
• Relying solely on ESR for diagnosis (can be normal in some GCA cases)
• Failing to evaluate for large vessel involvement in newly diagnosed cases
• Inadequate biopsy specimen length (<1 cm) reducing diagnostic yield 1