Validity of the EULAR recommendations on the use of ultrasound in the diagnosis of giant cell arteritis

Objectives The European Alliance of Associations for Rheumatology (EULAR) recommendations for the use of imaging in large vessel vasculitis establish that an imaging test supported by clinical pretest probability (PTP) is sufficient for the diagnosis of giant cell arteritis (GCA). Our objective was to determine the validity of the EULAR recommendations on the use of Colour duplex ultrasound (CDUS) in GCA after calculating the PTP. Methods We collected data of all patients referred to our fast-track clinic between 2016 and 2020. The Southend pretest probability score (SPTPS) was calculated and classified as low (LR), intermediate and high risk (HR) according to the values obtained by its authors, <9, 9-12 and >12, respectively. All patients underwent a CDUS of the temporal arteries with their common, parietal and frontal branches, and the most also axillary (86.5%), and subclavian and carotid arteries. The gold-standard diagnosis was made according to the physician's criteria after at least 9 months of follow-up. Results Of the 297 referred patients, 97 (32.7%) were diagnosed with GCA. The SPTPS area under the ROC curve was 0.787. The LR category included 105 patients (35.4%), of which 10 (9.5%) had GCA and 1 had a CDUS false negative result. The HR category included 67 patients (22.5%), 47 with GCA, and in 1 case the CDUS result was a false positive. Conclusion Combining the results of a PTP score, such as SPTPS, and the CDUS allows for an accurate diagnosis of GCA, as established by the EULAR group, with less than 2% misclassification of diagnosis.