In vitro assays to test the interference of anti-thyroglobulin antibodies on thyroglobulin measurement

• DOI: 10.1007/s12020-008-9053-2
• Publication Date: 2008-03-28T20:03:37Z
• Authors: Deolinda Madureira; Susana Prazeres; Márcia São Pedro; Teresa Pereira; Ana Paula Font; Maria João Bugalho
• Keywords: Thyroglobulin; Serial dilution; Dilution

To assess the interference of anti-thyroglobulin antibodies (TgAb) on serum thyroglobulin (Tg) measurement by in vitro experiments. Design Re-evaluation of Tg concentration after dilution with different TgAb-positive sera. On a first step, dilutions of the same Tg with different TgAb sera were performed and on a second step, different Tgs were diluted with the same TgAb serum.Tg measurements were performed using an immunometric (IMA) chemiluminescence assay. TgAb measurements were performed using two methods: immunoflurimetric assay (UNICAP 100) and IMA chemiluminescent assay (IMMULITE 2000).Dilution of a known concentration of Tg with different TgAb-positive sera resulted in a variation of the final concentration of Tg ranging from -24 to -79%. A weak correlation was observed between the TgAb concentration and the percentage of the Tg deviation. Dilution of different Tgs with the same TgAb-positive serum illustrated how the same TgAb positive serum may determine a high interference or a neutral effect.Present results suggest that the interference on Tg measurement observed in the presence of TgAb may result not only from the anti-thyroglobulin antibodies, but also from the thyroglobulin itself.