Longitudinal change of postoperative serum anti-thyroglobulin antibody levels in patients without total thyroidectomy and remnant ablation
Backgroud: There is little information regarding postoperative anti-thyroglobulin antibody (TgAb) changes in patients without a total thyroidectomy and ablation. This study aimed to analyze the longitudinal change of TgAb levels in patients with remnant thyroid. Methods: The study group were patients who had undergone a non-total thyroidectomy for papillary thyroid carcinoma from 1996 to 2018. The median follow-up period of measurement serum Tg and Tg Ab was 3.5 years (1-7.5 years). Eligible patients had a combined serum Tg and TgAb measurement at least three times biannually. We excluded patients with thyroid dysfunction at the initial diagnosis or with papillary carcinoma who had persistent or any recurrence of disease. Results: A total of 209 patients were enrolled. In the preoperative analysis, 41 (31%) patients had positive TgAb values, and 91 were negative (69%). Seventeen years after the operation, a TgAb value over 800 IU/ml was not seen. The positive TgAb ratio was stable for 12 years (20%-30%); however, its positivity gradually increased from 13 years onward to 45.5%. The number of patients with consistently negative and positive TgAb values was 140 (67.0%) and 47 (22.5%), respectively. The number of patients with a mixture of positive and negative TgAb values was 10 (4.8%). The number of patients who changed from positive to negative values was six (2.9%) and, inversely, six (3.9%). Conclusions: We found positivity of TgAb after surgery gradually increases up to 45.5% over about 10 years in patients with normal remnant thyroid. We might continue to measure both serum Tg and TgAb values concurrently for the patients with remnant thyroid tissue throughout.