Assessment of the utility of measuring Thyroglobulin mRNA levels by Quantitative Real-Time PCR in the follow-up of differentiated thyroid cancer patients

Introduction: The determination of thyroglobulin (Tg) levels by immunoassay is subject to interference by antithyroglobulin antibodies in up to 30% of cases, suggesting a need to find alternative methods for the follow-up of a significant number of thyroid cancer patients. Objectives: Assess the sensitivity, specificity, and predictive values of thyroglobulin messenger RNA (Tg-mRNA) levels measured by quantitative Real Time-PCR (qRT-PCR) in the blood of patients followed for differentiated thyroid cancer. Methods: This is a prospective study of Tg-mRNA levels measured with qRT-PCR. A peripheral blood sample was taken in patients with excellent response (n = 69) and with structural incomplete response to treatment (n = 23). Results were analysed using the Unity Real-Time program and expressed as fg/mu g RNA. A Receiver Operating Characteristic curve was constructed to establish Tg-mRNA cut-off values. Results: Tg-mRNA levels were not significantly different between the group with excellent response [0.10 fg/mu g RNA (0.08-0.17)] and the group with incomplete structural response [0.133 fg/mu g RNA (0.07-0.33)] (p < 0.06). Test sensitivity was 69.6%, specificity was 59.4%, negative predictive value was 85.4% and positive predictive value was 36.4%. Conclusions: Our experience shows that this technique could be useful as a rule-out test in selected cases, but its low sensitivity and specificity preclude its usefulness as a first-line test. (c) 2021 SEEN y SED. Published by Elsevier Espana, S.L.U. All rights reserved.