Clinical utility of an ultrasensitive thyroglobulin assay in the follow-up of patients with differentiated thyroid cancer: can the stimulation test be avoided in patients with an intermediate recurrence risk?

• Published in: Acta otorhino-laryngologica italica 2018-06, Vol.38 (3), p.188-193
• Main Authors: Flores-Rebollar, A, Pérez-Díaz, I, Lagunas-Bárcenas, S, García-Martínez, B, Rivera-Moscoso, R, Fagundo-Sierra, R
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Child; Female; Follow-Up Studies; Head and Neck; Humans; Male; Middle Aged; Neoplasm Recurrence, Local - blood; Neoplasm Recurrence, Local - epidemiology; Predictive Value of Tests; Retrospective Studies; Risk Assessment; Sensitivity and Specificity; Thyroglobulin - blood; Thyroid Neoplasms - blood; Thyroid Neoplasms - epidemiology; Thyroid Neoplasms - pathology; Young Adult
• ISSN: 1827-675X; 0392-100X; 1827-675X
• DOI: 10.14639/0392-100X-1494

Serum thyroglobulin (Tg) measurement during suppression with levothyroxine (LT4) using an ultrasensitive assay (OnT4-Tg) has been proposed as a replacement of TSH-stimulated Tg measurement (OffT4-Tg) in management of patients with differentiated thyroid cancer (DTC). The aim of this study is to evaluate the capacity of an ultrasensitive Tg assay in predicting an OffT4-Tg > 2.0 ng/mL based on the OnT4-Tg in patients with DTC and an intermediate recurrence risk. We analysed 101 patients with DTC and an intermediate (n = 92) or high risk of recurrence (n = 9) who were treated with total thyroidectomy and ablation with I, and followed for an average of 6 years. OnT4-Tg was undetectable in 64 of 101 patients; OffT4-Tg was #x003C; 2.0 ng/mL in 61 of these 64 patients, all with negative imaging results. Furthermore, 37 of 101 patients had detectable OnT4-Tg; 32 of these 37 patients also presented OffT4-Tg > 2.0 ng/mL, and only 3 of these 32 patients had metastases detected by neck ultrasound. Considering a cutoff point of 0.1 ng/mL for OnT4-Tg, the assay had a sensitivity of 91%, specificity of 92%, positive predictive value (PPV) of 86% and the negative predictive value (NPV) of 95% when predicting an OffT4-Tg > 2.0 ng/mL (biochemical disease). The use of an ultrasensitive Tg assay allows prediction of which patients will remain disease-free even if they are at an intermediate risk of recurrence, and to decrease the need for stimulated Tg assays in two-thirds of these patients.