Clinical value of M22-based assays for TSH-receptor antibody (TRAb) in the follow-up of antithyroid drug treated Graves' disease: Comparison with the second generation human TRAb assay.

摘要

BACKGROUND: We compared the clinical performances of two new M22-based assays for TSH-receptor antibody (TRAb) with those of the human TRAb assay (hTRAK) in Graves' disease patients at the end of treatment. PATIENTS AND METHODS: Sera were obtained from 128 Graves' patients treated for 18 months with antithyroid drugs. Sixty-six remained in remission and sixty-two had relapse of hyperthyroidism in a 3-year follow-up after discontinuing treatment. TRAbs were measured using two M22-based methods (electrochemiluminescence using the Cobas or ELISA using the Medizym TRAb clone) and with the hTRAK. RESULTS: At T18, the results were significantly higher by the Cobas assay (median: 2.7 IU/L, range: 1.1-18.5 IU/L) or lower by ELISA (median: 0.56 IU/L, range: 0.22-14.8 IU/L) than those obtained for the hTRAK (median: 1.5 IU/L, range: 0.9-9.8 IU/L). The use of cut-off limits at 1.9 IU/L, 3.2 IU/L and 0.94 IU/L gave similar and higher prevalences of TRAb-positive patients in the group of relapse as compared to the remission group. However, some patients remained misclassified in each remission or relapse group. CONCLUSIONS: The M22-based TRAb assays did not improve the predictive value of relapse obtained with the hTRAK measured at the end of treatment. High inter-method variability requires assay harmonization for correct interpretation of results.