The Diagnostic Value of Serum TgAb in the Tg-Negative and TgAb-Positive DTC Patients after Successful Ablation

Abstract

Objective: The aim of this retrospective study was to evaluate diagnostic accuracy of serum thyroglobulin antibody (TgAb) in thyroglobulin (Tg)-negative and TgAb-positive (Tg - TgAb + ) patients with differentiated thyroid carcinoma (DTC). Method: We studied 341 patients with histologically confirmed DTC who had undergone remnant ablation and showed Tg - TgAb + assessed by electrochemiluminescence immunoassay (ECLIA). The cases were divided into two groups, including recurrence group 119 cases and no evidence of disease (NED) group 222 cases. Receiver operating characteristic (ROC) curve analysis was carried out. The symmetric measures of the two diagnostic methods (the golden standard and the diagnostic standard as serum TgAb level alone) were analyzed using McNemar test and measure of agreement Kappa. Results: Serum TgAb level (1381.292 ± 1017.221) IU/ml of patients with recurren t group was significantly higher than that (125.559 ± 314.047) IU/ml of NED group (P = 0.000 < 0.001). The area under the ROC curve was 0.962 and its asymptotic 95% confidence interval (CI) was (0.942 , 0.982) that was high statistical significance. The cut-off value of TgAb was determined and interpreted at 246.695 IU/ml with sensitivity (92.40%) and specificity (92.30%). McNemar test showed that the diagnostic results of the two methods were not significant difference (P = 0.230 > 0.05). Measure of agreement Kappa was 0.841, P = 0.000 < 0.001 that showed the agreement of the two diagnostic methods was significan t . Conclusion: Serum TgAb is a useful tumor marker for recurrence in Tg-negative and TgAb-positive DTC patients who underwent thyroidectomy and remnant ablation. The cut-off value of TgAb is 246.695 IU/ml, that is to say, serum TgAb level upon 246.695 IU/ml may be associated with the persistence or recurrence of DTC.