Laboratory services for thyroglobulin and implications for monitoring of differentiated thyroid cancer.

Serum thyroglobulin is used as a marker for monitoring differentiated thyroid cancer. There are a number of analytical challenges: the need for stability of the assay over decades, differences in assay bias, and interference in immunoassays by endogenous thyroglobulin antibodies. Improved precision at low analyte concentrations is desirable. Approaches to identifying assay interference are discussed. No single approach is likely to be successful on all occasions. Decision limits should be assay-specific, and clinicians should be aware of the limitations of current immunoassays.