From the Guidelines
Diagnosing Giant Cell Arteritis (GCA) requires a combination of clinical assessment, laboratory tests, and imaging studies, with a focus on prompt initiation of empiric high-dose corticosteroid therapy when GCA is strongly suspected, as recommended by the 2021 American College of Rheumatology/Vasculitis Foundation guideline 1. The diagnosis should begin with a thorough history and physical examination, focusing on symptoms like new-onset headache, scalp tenderness, jaw claudication, visual disturbances, and constitutional symptoms such as fever, weight loss, and fatigue.
- Laboratory tests are essential, particularly erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are typically elevated in GCA, as noted in a systematic review and meta-analysis published in JAMA Internal Medicine 1.
- A complete blood count may show normocytic anemia.
- The gold standard for diagnosis remains temporal artery biopsy, which should be performed within 1-2 weeks of starting corticosteroid therapy to avoid false-negative results, as suggested by the guideline 1.
- The biopsy should be at least 1-2 cm in length due to the skip lesions characteristic of GCA.
- When biopsy is not feasible or results are negative despite high clinical suspicion, imaging studies like color duplex ultrasonography, high-resolution MRI, or PET-CT can be valuable alternatives, as recommended by the guideline 1.
- These imaging techniques can detect vessel wall inflammation in cranial and extracranial arteries.
- Prompt diagnosis is crucial as GCA can lead to irreversible vision loss if treatment is delayed, so empiric high-dose corticosteroid therapy (prednisolone 40-60 mg daily) should be initiated immediately when GCA is strongly suspected, even before confirmatory tests are completed, as emphasized by the guideline 1 and supported by the systematic review and meta-analysis 1.
From the Research
Diagnosis of Giant Cell Arteritis (GCA)
To diagnose GCA, several methods can be employed, including:
- Temporal artery biopsy, which remains the gold standard for diagnosis 2, 3, 4
- Laboratory tests, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels, although these can be normal in some cases 2
- Imaging studies, including:
- Clinical evaluation, including physical examination and medical history 3, 5
Diagnostic Challenges
GCA diagnosis can be challenging due to:
- False negatives from temporal artery biopsy due to the segmental nature of the disease, inadequate vessel length, or inadequate interpretation 3
- Normal ESR and CRP levels in some patients with GCA 2
- Variability in clinical presentation 5
Alternative Diagnostic Methods
Some studies suggest that duplex ultrasound of carotid arteries can be an effective alternative to temporal artery biopsy 3, while others highlight the importance of advanced arterial imaging in diagnosing GCA 6, 5.