External validation of the GREAT score to predict relapse risk in Graves’ disease: results from a multicenter, retrospective study with 741 patients

Context First-line treatment in Graves’ disease is often done with antithyroid agents (ATD), but relapse rates remain high making definite treatment necessary. Predictors for relapse risk help guiding initial treatment decisions. Objective We aimed to externally validate the prognostic accuracy of the recently proposed Graves’ Recurrent Events After Therapy (GREAT) score to predict relapse risk in Graves’ disease. Design, setting and participants We retrospectively analyzed data (2004–2014) of patients with a first episode of Graves’ hyperthyroidism from four Swiss endocrine outpatient clinics. Main outcome measures Relapse of hyperthyroidism analyzed by multivariate Cox regression. Results Of the 741 included patients, 371 experienced a relapse (50.1%) after a mean follow-up of 25.6 months after ATD start. In univariate regression analysis, higher serum free T4, higher thyrotropin-binding inhibitor immunoglobulin (TBII), younger age and larger goiter were associated with higher relapse risk. We found a strong increase in relapse risk with more points in the GREAT score from 33.8% in patients with GREAT class I (0–1 points), 59.4% in class II (2–3 points) with a hazard ratio of 1.79 (95% CI: 1.42–2.27, P