Circulating thyrotropin receptor messenger ribonucleic acid is not an effective marker in the follow-up of differentiated thyroid carcinoma

BACKGROUND Circulating thyrotropin receptor messenger ribonucleic acid (TSHR mRNA) assay has been validated in the follow-up of differentiated thyroid carcinoma (DTC) because of its high sensitivity during thyroid hormone therapy and no interference with endogenous anti-thyroglobulin antibodies (TgAb) compared to serum thyroglobulin (Tg). We investigated the efficacy of TSHR mRNA assay in 160 DTC patients using quantitative PCR (qPCR). FINDINGS Only TSHR mRNA level of structural persistent disease with TgAb-positive (3.47 (2.97-9.53) pg equivalents/μg total RNA; p = 0.013) and its subgroup of distant metastasis patients with TgAb-positive (5.55 (3.28-12.52) pg equivalents/μg total RNA; p = 0.009) were significantly different from patients with no evidence of disease (2.32 (1.44-3.94) pg equivalents/μg total RNA). Applying cutoff at 2.00 pg equivalents/μg total RNA enabled us to predict structural persistent disease patients with a sensitivity of 62.3 % and a specificity of 42.9 %. Although, the sensitivity of TSHR mRNA assay in TgAb-postive patients (88.2 %) was superior than serum Tg (47.1 %) (p = 0.00002), the accuracy of the test is only 54.5 %. CONCLUSIONS This study demonstrated that TSHR mRNA assay has good sensitivity in TgAb-positive patients but it is neither specific enough as a first-line of testing nor a surrogate marker in the follow-up of our DTC patients.