Evaluation of the BRAHMS Kryptor® Thyroglobulin Minirecovery Test in patients with differentiated thyroid carcinoma

Abstract

The present study was undertaken to evaluate a new sensitive thyroglobulin (Tg) mini-recovery test (Tg-mrec) for the detection of potential interferences in sera from patients with differentiated thyroid carcinoma (DTC) and low Tg levels. 167 DTC patients with serum Tg <2 μg/L were enrolled. Both TgAb and Tg-mrec measurements were performed on the automated Kryptor(®) platform. Serum pretreatment in proprietory blocking tubes was perfomed to screen for heterophile antibody interferences. The concordance rates between tests were evaluated. One case of over-recovery occurred in a patient with discordant Tg results in different immunoassays. The prevalences of a positive TgAb test and a reduced recovery rate were 15%-12%, respectively. Serum TgAb and Tg-mrec tests were both positive in 16 patients, both negative in 138 patients and discordant in 13 patients, respectively. The concordance rate between the Tg-mrec test and the TgAb assay was 92% (Cohens' kappa 0.894; 95% confidence interval: 0.82-0.93, p<0.001). In all, among seven clinically relevant interferences, three were found by TgAb, five by Tg-mrec and six by using both tests. The automated Kryptor(®) Tg-mrec test has a complimentary value to TgAb immunoassay testing in the detection of potential interferences in Tg measurements in patients with DTC and low Tg values (i.e., <2 μg/L). Tg-mrec may detect interferences from TgAb not measured directly by an individual TgAb assay or from other interfering substances, such as heterophile antibodies.