Objectives: Thyroglobulin (Tg) is a key tumor marker for monitoring differentiated thyroid carcinoma (DTC). At our center, ~5,000 samples are analyzed annually using a rapid, sensitive, automated, and cost-effective in-house immunoradiometric assay (IRMA). Tg assays, however, may yield falsely low results due to interference from Tg autoantibodies (TgAb) or the high-dose hook (HDH) effect. TgAb interference is identified with recovery tests, whereas the HDH effect is best detected by comparing undiluted and diluted samples. The present study evaluates the utility of a Tg recovery test for detecting HDH in serum Tg measurements using an in-house IRMA, thereby ensuring accurate Tg estimation in patients with DTC. Material and Methods: Present retrospective analytical study demonstrates application of the conventional Tg recovery test for simultaneous detection of TgAb interference and HDH effect in 2389 DTC patients using the indigenous Tg IRMA kit. The Tg recovery test was performed by spiking a known concentration of Tg into each patient serum sample and measuring the % recovery. The patients were screened from the electronic database. Results: We have presented analysis of 2389 patient sample results and detected a significant presence of hook effect in 91 (3.8%) samples compared to TgAb interference in 24 (1%) samples by “recovery test.” Conclusion: We mention an additional use of a routine, simple, inexpensive Tg recovery assay in complement for the simultaneous detection of Tg values using an indigenous IRMA kit to identify the recurrent or metastatic disease in DTC patients to avoid a delayed diagnosis and further possible medical inferences.
Gholve et al. (Sat,) studied this question.