Predictive value of antithyroglobulin antibody on recurrence or metastasis following ablation in differentiated thyroid carcinoma

Objective To investigate the value of serum thyroglobulin (Tg) and antithyroglobulin antibody (TgAb) in differentiated thyroid carcinoma complicated with Hashimoto's thyroiditis after thyroid ablation.Methods Serum Tg and TgAb levels and the status of illness in 154 differentiated thyroid carcinoma patients with coexistent Hashimoto's thyroiditis and confirmed pathology after surgery followed by remnant ablation were performed during three years follow up.Tg and TgAb levels were assessed by chemiluminescent immunoassay assay.The cases were divided into three groups (according to the level of Tg):Tg ≤ 1 μg/L group,1 μg/L＜Tg ≤ 10 μg/L group and 10 μg/L＜Tg≤ 100 μg/L group.TgAb＞40 kIU/L was considered as positive,Cox's proportional hazard model was used to analyse prognostic value in different levels of Tg and TgAb for disease-free survival and recurrence.Results Compared with 1 μg/L＜Tg≤ 10 μg/L group and 10 μg/L＜Tg≤ 100 μg/L group,the relative risk in reflecting cancer recurrence (TgAb＞40 kIU/L) in Tg ≤ 1 μg/L group was 27.000 (95 ％ CI 6.727-108.374).The value of TgAb＞40 kIU/L in Tg≤ 1 μg/L group was greatly increased and highly correlated with metastasis.However,In the condition of Tg＞ 1 μg/L,the disease will be based on the level of TgAb.Conclusion The value of TgAb＞40 kIU/L in Tg ≤ 1 μg/L group seems to be the optimal cutoff value correlated with recurrence and metastasis of differentiated thyroid carcinoma. Key words: Thyroid carcinoma ;  Hashimoto's thyroiditis ;  Thyroglobulin ;  Antithyroglobulin antibody