Serum thyroglobulin measurement in the follow-up of patients treated for differentiated thyroid cancer.

Determination of thyroglobulin (Tg) in serum represents a key element in the follow-up of patients treated for differentiated thyroid cancer (DTC). The sensitivity and the specificity of the assay strongly affects the clinical impact. Most of patients are disease-free after thyroidectomy and iodine radioablation; 15% of them show over time persistent or recurrent disease; of these, 5% dies due to worsening of disease. This implies that the follow-up procedures should have a high negative predictive value to reduce as possible the unnecessary diagnostic tools and a high positive predictive value to identify the few patients with persistent/recurrent disease. The recent international guidelines are based on thyroglobulin measurement after thyroid-stimulating hormone (TSH) stimulation. More recent studies suggest that follow up based on serial measurements of basal (i.e. unstimulated) Tg show a higher predictive value than the single measurement after stimulation. Large and multi-center studies are necessary to modify the current guidelines.