Ultrasound for the Diagnosis of Giant Cell Arteritis.

Giant cell arteritis (GCA) is the most frequent large vessel primary vasculitis in the elderly. Correct diagnosis and fast assessment are necessary to prevent complications as well as unnecessary treatments. Giant cell arteritis can present as classical cranial symptoms or as extracranial disease. Although temporal artery biopsy is still the gold standard, ultrasound (US) is gaining ground on evidence with good diagnostic performance as a first approach to support the clinical criteria. The "halo" sign is the most characteristic finding and should be a requisite for reporting an US assessment for GCA with a 43%- 77% sensitivity and 89%-100% specificity, when compared to American College of Rheumatology 1990 criteria. Ultrasound is a cost-effective, noninvasive test that offers bed-side results. The need for an experienced sonographer and consensus on the methodology and interpretation of US is fundamental to reduce operator-dependent errors. The diagnostic US algorithm for GCA depends on the clinical scenarios, and in some cases it may be enough to confirm or discard the GCA diagnosis. We review procedure details for cranial and extracranial arteries and technical requirements.