Additional value of a high sensitive thyroglobulin assay in the follow-up of patients with differentiated thyroid carcinoma.

OBJECTIVE: Thyroglobulin (Tg) is an excellent tumour marker, as detectable or increasing Tg levels are highly indicative of persistent or recurrent differentiated thyroid carcinoma (DTC). The clinical value of a highly sensitive (hs)-Tg assay in patients with DTC has not yet been established. The aim of this study was to investigate the additional value of unstimulated hs-Tg measurements (Tg-on) compared to stimulated IRMA-Tg measurements (Tg-off) in the follow-up of patients with DTC. DESIGN, PATIENTS, MEASUREMENTS: We retrospectively studied patients treated for DTC between 2006 and 2013 and compared hs-Tg and IRMA-Tg measurements. The study group consisted of 99 DTC patients in remission; Tg-on was measured 3 months after remnant ablation and Tg-off 6 months after ablation. RESULTS: In the study group, 44 patients showed a hs-Tg-on <0·15 µg/l (functional sensitivity); of these, 43 had an IRMA-Tg-off measurement <1·0 µg/l, resulting in a negative predictive value of 97·7% and a positive predictive value of 56·4%. CONCLUSIONS: The hs-Tg-on measurement is able to predict patients with an IRMA-Tg-off <1·0 µg/l, and therefore decreases the need for Tg stimulation after ablation.