What is the recommended workup and treatment for a patient suspected of having Giant Cell Arteritis (GCA)?

Workup for Giant Cell Arteritis (GCA)

Initial Clinical Assessment and Laboratory Testing

When GCA is suspected, immediately obtain ESR, CRP, and complete blood count before initiating treatment. 1, 2, 3

Essential Laboratory Markers

• ESR and CRP are complementary and both should be obtained - they provide independent diagnostic information and are elevated in the majority of GCA cases 1, 2
• An ESR >100 mm/h has a positive likelihood ratio of 3.11 for GCA, while a normal ESR (<40 mm/h) strongly argues against the diagnosis (negative likelihood ratio 0.18) 1
• A normal CRP (<2.5 mg/dL) similarly argues against GCA with a negative likelihood ratio of 0.38 1
• Platelet count >400 × 10³/μL supports GCA with a positive likelihood ratio of 3.75 1
• Recent evidence suggests ESR may not add diagnostic value beyond platelet count and CRP - initial biochemical evaluation can be based on platelet count and CRP alone, allowing faster decision-making without waiting for ESR results 4

Key Clinical Features to Assess

• Jaw claudication (positive likelihood ratio 4.90) and limb claudication (positive likelihood ratio 6.01) are the strongest clinical predictors 1
• Temporal artery abnormalities including thickening, loss of pulse, or tenderness 1
• Consider GCA even without typical temporal headache if the patient presents with limb claudication, constitutional symptoms alone, large vessel involvement, polymyalgia rheumatica symptoms, or unexplained stroke/cerebral ischemia in patients over 50 years 1
• Age under 50 is a strong negative predictor that should prompt consideration of alternative diagnoses 5

Temporal Artery Biopsy

Temporal artery biopsy remains the gold standard for diagnosis in the United States and should be obtained as soon as possible. 6

Biopsy Technique and Timing

• Obtain a long-segment biopsy (>1 cm) rather than short-segment (<1 cm) - GCA is a focal and segmental disease, and longer segments maximize diagnostic yield with minimal added morbidity 6
• Perform unilateral temporal artery biopsy initially rather than bilateral biopsies 6
• Obtain the biopsy within 2 weeks of starting glucocorticoids - histopathologic changes are more likely to be detected within this timeframe, though changes can be detected even later 6
• Do not delay treatment to obtain biopsy - start glucocorticoids immediately when GCA is suspected, then arrange biopsy 6, 2, 3

Alternative to Biopsy

• Temporal artery ultrasound may be used in centers with appropriate expertise, but biopsy remains optimal in the US where ultrasound experience is more limited and results are operator-dependent 6
• MRI of cranial arteries is not preferred over temporal artery biopsy for establishing diagnosis 6

Large Vessel Imaging

For patients with suspected GCA and negative temporal artery biopsy, obtain noninvasive vascular imaging of the large vessels to aid in diagnosis. 6

• For patients with newly diagnosed GCA, obtain noninvasive vascular imaging to evaluate large vessel involvement - this helps assess disease extent and guide management 6
• Large vessel involvement may be present even without cranial symptoms 1, 7

Treatment Initiation (Part of Diagnostic Workup)

Start high-dose glucocorticoids immediately when GCA is suspected, even before diagnostic confirmation. 1, 2, 3

Standard Treatment Protocol

• For suspected GCA without vision loss: initiate oral prednisone 40-60 mg/day 1, 7
• For threatened vision loss or active visual symptoms: start IV methylprednisolone (250 mg every 6 hours) for 3-5 days, then transition to oral prednisone 1, 3
• Add low-dose aspirin (100 mg daily) for patients with critical or flow-limiting involvement of vertebral or carotid arteries 1, 3

Common Pitfall

Do not wait for biopsy results or imaging before starting treatment - the risk of irreversible vision loss far outweighs any reduction in biopsy sensitivity from early glucocorticoid therapy 6, 2, 3

Monitoring After Diagnosis

Patients with GCA require long-term clinical monitoring including history, examination, and laboratory studies - this is a strong recommendation given potential catastrophic outcomes without monitoring 6

• Monitor ESR and CRP during follow-up to guide glucocorticoid tapering 2, 3
• Isolated elevation of inflammatory markers without clinical symptoms does not warrant escalation of immunosuppressive therapy - observe and monitor more frequently instead 6