ObjectiveTo evaluate the impact of a standardised training programme including equipment adjustment for experienced musculoskeletal ultrasonographers without previous experience in vascular ultrasound (US) on the reliability of US in the diagnosis of giant cell arteritis (GCA).MethodsIn this prospective, non-interventional observational cohort study, patients suspected of GCA were evaluated by US by one of five rheumatologists with long-standing experience in musculoskeletal US (>8 years), trained using a standardised training programme including equipment adjustment. Images of cranial and large vessels were subsequently evaluated first by the performing ultrasonographer and thereafter by a blinded external expert (gold standard).ResultsIn three Danish centres, 112 patients suspected of GCA were included. According to the external expert, vasculitis changes were seen in 66 patients, in 45 of them with only cranial involvement, in 14 with both cranial and large vessel involvement, while in seven patients isolated large vessel vasculitis was found. The reliability was excellent between the local ultrasonographer and the US expert for the overall GCA diagnosis regarding the diagnosis of cranial and for large vessel GCA, with an interobserver agreement of 95–96%, mean kappa values of 0.88–0.92 (95% CI 0.78 to 0.99). Excellent reliability (mean kappa 0.86–1.00) was also found for the US examination of the individual arteries (temporal, facial, common carotid and axillary).ConclusionThe US training programme resulted in excellent agreement between trainees and an expert in patients suspected of GCA and may thus be applicable for implementation of vascular US in clinical practice.