ObjectiveThe main study objective was to determine how giant cell arteritis (GCA) is diagnosed in our clinical practice and whether the EULAR recommendations have influenced the diagnostic procedures used.MethodsARTEritis of the Rheumatology Spanish Society -Sociedad Española de Reumatología (ARTESER) is a multicentre observational retrospective study conducted in 26 hospitals with support from the Spanish Society of Rheumatology. All patients diagnosed with GCA between 1 June 2013 and 29 March 2019 were included. The gold standard for the diagnosis of GCA was the judgement of the physician in charge, according to clinical criteria, supported by data available from laboratory tests, imaging studies (ultrasound, positron emission tomography (PET) and MRI/CT angiography) and temporal artery biopsy (TAB) when available.ResultsWe included 1675 patients with GCA (mean age±SD (76.9±8.1) years, 1178 women (70.3%)). Of these, 776 patients had a positive TAB (46.3%), 503 (30.0%) positive ultrasound, 245 positive PET (14.6%) and 64 positive MRI/CT angiography (3.8%). These percentages changed substantially over the study. From 2013 to 2019, the use of ultrasound in diagnosis grew from 25.8% to 52.9% and PET from 12.3% to 19.6%, while use of TAB decreased from 50.3% to 33.3%.ConclusionsBiopsy was the most widely used diagnostic test for confirming GCA, but use of imaging as a diagnostic tool has grown in recent years. Following publication of the 2018 EULAR recommendations, ultrasound has displaced biopsy as the first-line diagnostic test; TAB was performed in a third and PET in a fifth of cases.