The liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to overcome interference from thyroglobulin autoantibodies (TgAb); however, it has not yet been implemented in Korea. This study aimed to confirm the accuracy of LC-MS/MS compared to conventional methods and to identify its advantages in patients with thyroid carcinoma (TC). A total of 206 TC and 18 Hashimoto's thyroiditis samples were collected. TgAb-positive (TgAb-P) was defined as TgAb >60 U/mL. Tg testing was performed using LC-MS/MS, immunoradiometric assay (Tg-IRMA), and chemiluminescence microparticle immunoassay (Tg-CMIA). The interference of TgAb in LC-MS/MS and CMIA methods was evaluated through an in vitro TgAb spiking experiment. The frequency of TgAb-P in TC samples was 76.2%. Correlations between assays were as follows: Tg measurements made by LC-MS/MS (Tg-MS) and Tg-IRMA (R=0.93), Tg-MS and Tg-CMIA (R=0.96), and Tg-CMIA and Tg-IRMA (R=0.99), and it was lower in TgAb-P than TgAb-negative group. Clinical factors (total thyroidectomy, thyroid lobectomy, and Hashimoto's thyroiditis) did not affect these correlations. In TgAb spiking experiments, Tg-CMIA showed false negatives in TgAb-P, whereas Tg-MS did not. Among 21 TC cases with highly suspicious disease recurrence but Tg-IRMA <1 ng/mL, Tg-MS detected Tg ≥0.5 ng/mL in six samples. However, there was no consistent pattern of recurrence or TgAb trends. Correlations between assays were lower in TgAb-P cases. The spike test results show Tg-MS is less prone to false negatives in TgAb-P cases. Tg-MS may improve Tg detection in TgAb-P cases. However, we could not identify a distinct patient group with shared clinical features that would benefit from Tg-MS.
Park et al. (Tue,) studied this question.