The giant cell arteritis (GCA) ultrasound score (OGUS) at diagnosis and after initial treatment predicts future relapses in GCA patients: results of a multicentre prospective study

Objectives: To test the prognostic role of ultrasonography at diagnosis of giant cell arteritis (GCA) and the change of ultrasound abnormalities during the initial weeks of follow-up for the predic- tion of relapse, vascular complications, or initiation of disease-modifying antirheumatic drugs (DMARDs). Methods: Prospective, multicentre study of patients with new onset GCA undergoing serial ultra- sound assessment at fixed time points. The Outcome Measures in Rheumatology (OMERACT) GCA ultrasonography score (OGUS) was used to quantify vessel wall abnormalities. Relapse was defined as recurrence of GCA-related symptoms or rise of inflammatory markers requiring treat- ment. A multivariable Poisson model with robust variance estimator was applied, including age, sex, large vessel GCA, glucocorticoid cumulative dose, and baseline OGUS as covariates. Results: Ninety-seven patients were assessed in 849 visits. Thirty-five (36.1%) patients experi- enced a total of 66 relapses, with median time to relapse of 210 days (IQR, 94.5-323.5). Higher OGUS at diagnosis was associated with an increased risk of relapse within 12 months (incidence rate ratio [IRR] for each 1 point increase in OGUS: 1.85; 95% CI, 1.05-3.32). At multivariable analysis, OGUS normalisation (score <1) over the first 3 weeks was negatively associated with subsequent relapses (IRR, 0.44; 95% CI, 0.22-0.88) and predicted time to first relapse. OGUS reduction over the first 12 weeks was inversely associated with initiation of DMARDs. Ischae- mic/aortic complications were rare. Conclusions: Ultrasonography has a prognostic role in GCA and can inform risk stratification. Higher OGUS at diagnosis is associated with relapse, while a higher degree and rapidity of improvement in the first weeks are linked with lower relapse rate.