What is the appropriate workup for giant cell arteritis (GCA)?

Appropriate Workup for Giant Cell Arteritis (GCA)

The workup for giant cell arteritis should include a comprehensive clinical evaluation, laboratory testing, and temporal artery biopsy, with vascular imaging as a complementary tool to evaluate large vessel involvement. 1

Clinical Evaluation

• Assess for key symptoms associated with GCA diagnosis:

  • Jaw claudication (positive LR 4.90) 1
  • Limb claudication (positive LR 6.01) 1
  • Constitutional symptoms (fever, weight loss, malaise) 2
  • Visual disturbances (diplopia, vision loss) 2

• Perform physical examination focusing on:

  • Temporal artery thickening (positive LR 4.70) 1
  • Temporal artery loss of pulse (positive LR 3.25) 1
  • Temporal tenderness (positive LR 3.14) 1
  • Scalp tenderness (though less informative) 1

Laboratory Testing

• Obtain inflammatory markers:
  • Erythrocyte sedimentation rate (ESR) - absence of ESR >40 mm/h strongly argues against GCA (negative LR 0.18) 1
  • C-reactive protein (CRP) - absence of CRP >2.5 mg/dL argues against GCA (negative LR 0.38) 1
  • Complete blood count with platelet count - thrombocytosis >400 × 10³/μL supports GCA (positive LR 3.75) 1

Diagnostic Procedures

• Temporal artery biopsy:

  • Conditionally recommended over temporal artery ultrasound 1, 3
  • Obtain a long-segment specimen (>1 cm) for better diagnostic yield 1, 3
  • Perform within 2 weeks of starting glucocorticoids to maximize detection 1, 3
  • Unilateral biopsy is conditionally recommended over bilateral biopsies 1

• Vascular imaging:

  • Recommended for patients with negative temporal artery biopsy but high clinical suspicion 1, 3
  • Should be performed in all newly diagnosed GCA patients to evaluate large vessel involvement 1, 3
  • Options include ultrasound, MRI, CT, or PET 1, 4

Important Considerations

• No single clinical or laboratory feature is sufficient to rule in or rule out GCA; additional investigations are required 1
• Ultrasound is operator-dependent and results are influenced by glucocorticoid treatment, with signs of inflammation quickly disappearing after treatment initiation 3
• In centers with appropriate expertise, temporal artery ultrasound may be a useful complementary tool 3
• Age >70 years increases likelihood of GCA; absence of this feature decreases likelihood (negative LR 0.48) 1

Diagnostic Algorithm

1. Assess clinical features and obtain laboratory tests (ESR, CRP, CBC with platelets)
2. If clinical suspicion exists, initiate glucocorticoid therapy immediately if visual symptoms are present 5
3. Perform temporal artery biopsy within 2 weeks of starting glucocorticoids 1, 3
4. If biopsy is negative but clinical suspicion remains high, proceed with vascular imaging 1, 3
5. Evaluate for large vessel involvement with vascular imaging in all newly diagnosed cases 1, 3

Pitfalls to Avoid

• Do not rely solely on the American College of Rheumatology 1990 classification criteria for clinical diagnosis 1
• Do not delay treatment while awaiting biopsy if visual symptoms are present 5, 2
• Do not rule out GCA based on a single negative finding; consider the constellation of symptoms, signs, and laboratory results 1
• Do not wait longer than 2 weeks after starting glucocorticoids to perform temporal artery biopsy 1, 3