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 prediction of relapse, vascular complications, or initiation of disease-modifying antirheumatic drugs (DMARDs).

Methods: Prospective, multicentre study of patients with new onset GCA undergoing serial ultrasound 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 treatment. 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 experienced 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. Ischaemic/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.