Diagnosis of Giant Cell Arteritis
The diagnosis of giant cell arteritis requires a combination of clinical evaluation, blood tests, imaging, and—when needed—biopsy. Because giant cell arteritis can cause irreversible complications such as vision loss or stroke, early and accurate diagnosis is vital. Treatment is often initiated based on strong clinical suspicion even before confirmation, due to the high risk of delay.
This condition most commonly affects people over the age of 50, and the diagnostic process often begins when a patient presents with symptoms such as new-onset headache, jaw pain, or visual disturbances.
Clinical Evaluation
A detailed history and physical examination are the first steps. Key features that suggest GCA include:
New, persistent headaches in people over 50
Jaw claudication
Tenderness or thickening of the temporal arteries
Scalp sensitivity
Visual symptoms, such as blurred or double vision
Symptoms of polymyalgia rheumatica
On examination, doctors may find:
Thick, tender, or pulseless temporal arteries
Asymmetry in arterial pulses
Bruits (abnormal whooshing sounds) over large vessels
Signs of ischaemia, such as pale retina or afferent pupillary defect
Blood Tests
Although not diagnostic on their own, blood tests provide crucial supporting evidence.
1. Erythrocyte Sedimentation Rate (ESR)
Often markedly elevated (typically over 50 mm/hr)
Reflects systemic inflammation
2. C-Reactive Protein (CRP)
Sensitive marker for inflammation
May be raised even if ESR is normal
3. Full Blood Count
May show normochromic, normocytic anaemia
Thrombocytosis (elevated platelet count) is also common
These results support a clinical diagnosis and help rule out other causes.
Temporal Artery Biopsy
The gold standard for diagnosis is a temporal artery biopsy, which involves removing a small section of artery from the temple for microscopic examination.
Key findings include:
Granulomatous inflammation
Multinucleated giant cells
Intimal thickening and vessel wall disruption
While this is a highly specific test, false negatives can occur due to “skip lesions”, where inflammation affects segments of the artery unevenly. To reduce this risk, longer biopsy samples (2–3 cm) are preferred.
Biopsy should be performed within 1–2 weeks of starting steroids, as treatment can begin to reduce inflammatory changes quickly.
Imaging Studies
Modern imaging techniques have become valuable in both diagnosing and monitoring giant cell arteritis, especially in cases where biopsy is not possible.
1. Ultrasound (Colour Doppler)
Can detect the “halo sign”—a dark, hypoechoic ring around the artery indicating inflammation
Non-invasive, fast, and increasingly used as a first-line test
2. MRI or CT Angiography
Used to visualise larger arteries, such as the aorta or subclavian arteries
Helps assess extent of vessel involvement and detect complications like aneurysms
3. FDG-PET Scan
Useful in systemic or atypical cases
Detects increased metabolic activity in inflamed arteries
Expensive and less widely available
Diagnostic Criteria
The American College of Rheumatology (ACR) criteria for diagnosis include:
Age over 50
New-onset localised headache
Tenderness or decreased pulse in temporal artery
ESR > 50 mm/hr
Abnormal biopsy
Meeting three or more of these criteria yields high diagnostic accuracy, though real-world diagnosis often relies on a combination of clinical judgement and test results.
Differential Diagnosis
Conditions that can mimic GCA include:
Tension or migraine headaches
Dental infections
Trigeminal neuralgia
Carotid artery dissection
Meningitis or subarachnoid haemorrhage
These possibilities must be ruled out, especially when symptoms are non-specific or when typical GCA features are absent.
Initiating Treatment Before Confirmation
Due to the risk of permanent vision loss, treatment with high-dose corticosteroids should begin immediately if GCA is strongly suspected—even before biopsy or imaging confirmation.
Diagnosis of Giant Cell Arteritis
Delaying treatment can result in devastating consequences, and early steroid use does not invalidate a biopsy for at least 7–10 days.
