Significance of simultaneous measurement of serum thyroglobulin and thyroglobulin antibody during the follow-up of patients with differentiated thyroid carcinoma

Serum thyroglobulin is an essential marker during the follow-up of patients with differentiated thyroid carcinoma. Demonstration of the total absence of thyroglobulin is not possible by immunoanalytic methods if thyroglobulin antibody is present in serum samples that occur in almost 20% of patients with differentiated thyroid carcinoma. Therefore, current guidelines recommend estimation of thyroglobulin levels only if quantitative level of thyroglobulin antibody is known. However, normal thyroglobulin antibody level fails to exclude interference with the antibody, because antibody concentration within the normal range may interfere with the thyroglobulin assay. In this respect recommendations are not consistent because they distinguish only occasionally cases with normal and those with non-detectable serum thyroglobulin level. In addition, the possible impact of normal thyroglobulin antibody level on the thyroglobulin assay has not been entirely explored. Authors review literature data and current guidelines on the analytical and preanalytical limitations of the thyroglobulin and thyroglobulin antibody measurements. On the basis of their own studies, authors make recommendation for improvement of the diagnostic accuracy of the thyroglobulin measurement.