Which diagnostic test is used to confirm giant cell arteritis if suspicion is high?

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Temporal artery biopsy is the confirmatory test for giant cell arteritis when suspicion is high. This vasculitis involves the walls of medium-to-large arteries, and the only test that directly demonstrates the characteristic pathology is a biopsy of the temporal artery, showing transmural granulomatous inflammation with multinucleated giant cells and disruption of the internal elastic lamina. While ESR/CRP and clinical features strongly support the diagnosis and guide initial management, a biopsy provides definitive confirmation. Be aware that lesions can be patchy (skip lesions), so a longer, segmental sample improves yield, and a negative biopsy does not completely exclude disease if clinical suspicion remains high. Treat promptly with high-dose corticosteroids to reduce the risk of irreversible vision loss while awaiting biopsy results. The other tests listed—lumbar puncture, abdominal ultrasound, and MRI brain—do not diagnose GCA and are not used to confirm it.