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

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.; 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.; We retrospectively analyzed data (2004-2014) of patients with a first episode of Graves' hyperthyroidism from four Swiss endocrine outpatient clinics.; Relapse of hyperthyroidism analyzed by multivariate Cox regression.; 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 < 0.001) and 73.6% in class III (4-6 points) with a hazard ratio of 2.24 (95% CI: 1.64-3.06, P < 0.001).; Based on this retrospective analysis within a large patient population from a multicenter study, the GREAT score shows good external validity and can be used for assessing the risk for relapse in Graves' disease, which influence the initial treatment decisions.