Which test is best for confirming a diagnosis of giant cell arteritis?

The best method for confirming a diagnosis of giant cell arteritis is a temporal artery biopsy. This condition, also known as temporal arteritis, is an inflammatory disease that primarily affects the medium and large-sized blood vessels, particularly the temporal arteries.

A temporal artery biopsy involves the removal of a small section of the temporal artery, which is then examined histologically for the presence of giant cells, mononuclear infiltrate, and intimal thickness. The presence of these changes in the vessel wall is diagnostic for the condition and can confirm the suspicion raised by clinical symptoms and laboratory findings.

While blood tests such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are useful in suggesting inflammation, they are not definitive for giant cell arteritis. Imaging studies like CT or MRI can provide visual evidence of vascular inflammation but do not offer the histopathological confirmation that a temporal artery biopsy does. Therefore, biopsy remains the gold standard in diagnosing giant cell arteritis.