What is the workup for Giant Cell (GCA) Temporal Arteritis?

From the Guidelines

The workup for Giant Cell Arteritis (GCA) should begin with a thorough clinical evaluation, laboratory tests, and imaging studies, with temporal artery biopsy remaining the gold standard for diagnosis, ideally performed within 1-2 weeks of starting treatment, as recommended by the 2021 American College of Rheumatology/Vasculitis Foundation guideline 1. The initial workup should include erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are typically elevated, as well as a complete blood count, liver function tests, and platelet count.

• Key laboratory tests:
  • ESR
  • CRP
  • Complete blood count
  • Liver function tests
  • Platelet count
• Imaging studies may include color duplex ultrasonography of the temporal arteries, MRI, or CT angiography to identify large vessel involvement.
• Temporal artery biopsy is conditionally recommended over temporal artery ultrasound for establishing a diagnosis of GCA, with a long-segment temporal artery biopsy specimen (>1 cm) preferred over a short-segment temporal artery biopsy specimen (<1 cm) 1.
• The biopsy should be performed as soon as possible, ideally within 2 weeks of starting oral glucocorticoids, to maximize the likelihood of detecting histopathologic changes 1.
• Immediate treatment with high-dose corticosteroids should be initiated without waiting for biopsy results to prevent vision loss, with a typical regimen of prednisone 40-60mg daily (or equivalent) continued for 2-4 weeks before slow tapering over months 1.
• For patients with visual symptoms, consider IV methylprednisolone 500-1000mg daily for 3 days before transitioning to oral steroids, and steroid-sparing agents like methotrexate or tocilizumab may be added for long-term management 1.

From the Research

Diagnosis of Giant Cell Arteritis (GCA)

The diagnosis of GCA is primarily clinical, and several laboratory tests and procedures can support the diagnosis.

• Erythrocyte sedimentation rate (ESR) is often elevated, usually >50 mm/h, but a normal ESR does not rule out the disease 2, 3.
• C-reactive protein (CRP) may also be elevated, but a normal CRP does not exclude the diagnosis 3.
• Temporal artery biopsy (TAB) is considered the gold standard for diagnosis, but a negative biopsy does not rule out the disease due to skip lesions 3, 4, 5.
• The timing of TAB is crucial, and it is suggested to be performed within 2 weeks from the initiation of corticosteroids 6.

Clinical Presentation

GCA typically presents with symptoms such as:

• New-onset headache 4
• Jaw claudication 4
• Proximal myalgia 4
• Weight loss 4
• Fever 4
• Visual loss in one or both eyes due to AION or retinal artery occlusion 4

Treatment

Corticosteroids are the drug of choice to treat GCA, and therapy is required for a long time, monitored by parameters of inflammation (ESR, CRP) 4.

• High-dose steroids should be commenced promptly, even before performing a biopsy, if clinical suspicion is high 5.
• The duration of corticosteroid treatment may affect the positivity of TAB, with longer treatment duration potentially leading to lower rates of positive TAB 6.