engleski

SIGNIFICANCE OF THE "RECOVERY" TEST DURING THYROGLOBULIN CONCENTRATION MEASUREMENT

Serum thyroglobulin (Tg) is used as a sensitive and specific tumour marker in the postoperative follow-up of differentiated thyroid carcinoma (DTC). Various technical limitations of methods may compromise the reliability of measurement. Thyroglobulin autoantibodies (TgAb), even in very low concentrations, can interfere with Tg and thus under- or overestimate Tg. Immunometric tests (IMA) usually underestimate Tg-a when sera contain TgAb, presumably because the endogenous Tg complexed with TgAb cannot interact with the assay antibodies. In contrast, radioimmunoassay (RIA) may over- or underestimate Tg, depending on the assay architecture, i.e. the assay antibodies. The use of "recovery" test (Rc) may decrease the impact of TgAb interference on reliability. Low Rc values indicate the presence of TgAb in the sample (generally values lower than 80%) that interfered with the Tg determination, while values higher than 80% indicate undisturbed RC and thus a more reliable Tg. The usefulness of Rc for recognising Tg-TgAb interference has been disputed, because the epitopes of egzogenous Tg molecules (glandular origin) may differ from the epitopes of endogenous, tumorous Tg in the patients’ serum, that may be serologically unstable. The technical problem of epitope incompatibility in Rc may be solved by means of antibodies for Tg epitopes that endogenous TbAb cannot recognize, which would result in interference decrease

Serum thyroglobulin (Tg); tumour marker; differentiated thyroid carcinoma

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