Comparison of thyroglobulin antibody interference in first- and second-generation thyroglobulin immunoassays

Background: This study evaluated the impact of thyroglobulin (Tg) antibodies (TgAb) interference on Tg measurements performed with a second-generation immunometric Tg assay, in comparison to a first-generation method. Methods: Five serum pools without detectable TgAb and containing measurable Tg concentrations were obtained from DTC patients and mixed with sera from patients with measurable TgAb, but undetectable Tg concentrations. Tg and TgAb concentrations were measured by the first-and the second-generation Tg immunoassays and Tg-recovery was also evaluated for both assays. Results: The decrease in Tg concentrations in the presence of TgAb was more pronounced in the first-generation Tg assay (41.6%) compared with the second-generation assay (31.4%) (p < 0.01). Accordingly, the mean Tg-recovery values were 51.4% in the first-generation Tg assay and 68.8% in the second-generation (p < 0.01). Measurable Tg concentrations were found in all sera using the second-generation assay, but not the first-generation method. Conclusions: Our preliminary results indicate that an undetectabIe Tg concentration measured using the second-generation assay is unlikely to be a false-negative result induced by TgAb-interferences.