Does a Negative Thyroglobulin level Exclude Recurrence in Patients Treated for Differentiated Thyroid Neoplasm?

Introduction: Differentiated thyroid carcinomas (DTC) are the most common endocrine malignancy. Despite the good survival rate of these cancers, recurrence is still seen in practice. The recurrence sometimes is occult and the use of tumor marker like serum thyroglobulin level (Tg) could be helpful to predict any recurrent or persistent disease. Objectives: Our aim is to investigate the role of serum Tg as a single tumor marker to assess for any recurrent or residual disease in patients who were treated for DTC. Patients and methods: We performed a retrospective review for all patients who had DTC in our department over 7 years. We compared the levels of serum Tg with the recurrence rate. Our cut off value for Tg was 0.1 ug/L. Results: 102 patients (67 females and 35 males) with DTC were included in our study. Average age was 45.9 ±16 years of age. We reported a sensitivity rate of 100%, specificity was 97.9%, positive predictive value was 80%, negative predictive value was 100%, and diagnostic accuracy was 98%. Conclusion: With our cut off value of 0.1ug/L, serum Tg is an excellent negative predictor of the disease recurrence or persistence; however, with low levels (less than 0.5ug/L) further investigations are required to exclude a small tumor focus. Keywords: Thyroglobulin, differentiated thyroid carcinoma, recurrence, sensitivity, specificity, diagnostic accuracy