Monitoring differentiated thyroid cancer patients with negative serum thyroglobulin Diagnostic implication of TSH-stimulated antithyroglobulin antibody

Aim: Serum antithyroglobulin antibody (TgAb) has been reported as a surrogate marker for differentiated thyroid cancer (DTC) in some conditions. We investigated changes in serum TgAb levels after stimulation with thyroid-stimulating hormone (TSH) and the clinical implications for monitoring DTC. Patients, methods: We retrospectively enrolled 53 DTC patients who had undergone total thyroidectomy and were negative for serum Tg and positive for TgAb. Patients underwent high-dose radioactive iodine treatment, and serum TgAb was measured before (TgAb(BAS)) and after TSH stimulation (TgAb(STIM)). TgAb was followed up 6 to 12 months later (TgAb(F/U)). The change in TgAb after TSH stimulation (Delta TgAb(STIM)) was calculated as a percentage of the baseline level. Patient disease status was classified into no residual disease (ND) and residual or recurred disease (RD) by follow-up im aging studies and pathologic data. The characteristics and diagnostic value of serum TgAb levels and Delta TgAb(STIM) were investigated with respect to disease status. Results: 38 patients were in the ND group and 15 were in the RD group. TgAb(BAS), TgAb(STIM) and TgAb(F/U) were significantly higher in the RD compared to the ND group (p = 0.0008, 0.0002, and < 0.0001, respectively). Delta TgAb(STIM) was also significantly higher in the RD group (p = 0.0009). In the patients who presented with obviously high (>= 50%) or low (< -50%) Delta TgAb(STIM), the proportions in the RD group were markedly different at 100% and 7%, respectively. Delta TgAb(STIM) had significant diagnostic value for RD (p < 0.001). Conclusion: The change in serum TgAb level after TSH stimulation is different between the RD and ND groups, and thus, it may be used as a surrogate diagnostic marker for DTC when the serum Tg is negative and TgAb is positive.