Evaluation of the diagnostic performance of thyroid-stimulating immunoglobulin and thyrotropin receptor antibodies for Graves' disease.

OBJECTIVE: To evaluate thyroid-stimulating immunoglobulin (TSI) and thyrotropin receptor antibodies (TRAb) diagnostic performance for Graves' disease (GD) and determine clinical cut-off value for diagnosing GD.

METHODS: Of 1369 retrospectively enrolled subjects, 1364 had a definitive diagnosis of untreated GD (GD-UT, n = 87); treated GD (GD-T, n = 206); autoimmune thyroid disease (AIT, n = 241); thyroid nodules (TN, n = 677); subacute thyroiditis (ST, n = 28); healthy subjects (HS, n = 125); other diseases with serological hyperthyroidism (n = 5) and were grouped into the following: UT-GD and control groups (AIT, TN, ST, and HS); and UT-GD and non-GD hyperthyroidism groups. Diagnostic performance of TSI and TRAb was evaluated using area under the curve (AUC) of receiver-operating characteristic (ROC) curve, and optimal clinical cut-off value was determined using maximization of Youden index.

RESULTS: TRAb AUC and clinical cut-off value for diagnosing GD were 0.981 and 1.245 IU/L (sensitivity, 96.6%; specificity, 97.1%; positive predictive value [PPV], 71.8%; negative predictive value [NPV], 99.9%; positive likelihood ratio [PLR], 33.31; negative likelihood ratio [NLR, 0.035), respectively, for the GD-UT and control groups. Those for TSI were 0.992 and 0.467 IU/L (sensitivity 98.8%; specificity, 96.4%; PPV, 68.8%; NPV, 99.9%; PLR, 27.472; NLR, 0.011). Those for TRAb in GD-UT and non-GD hyperthyroidism groups were 0.923 and 1.78 IU/L (sensitivity, 92.0%; specificity, 89.1%; PPV, 93%; NPV, 87.5%; PLR, 8.44; NLR, 0.089), respectively. For TSI, these were 0.92 and 0.545 IU/L (sensitivity, 97.7%; specificity, 83.6%; PPV, 90.4%; NPV, 95.8%; PLR27.472, NLR, 0.011), respectively.

CONCLUSION: TSI diagnostic performance for GD was excellent and had better sensitivity than TRAb.