Critical aspects of immunoradiometric thyroglobulin assays.

BACKGROUND AND AIM OF THE STUDY

Thyroglobulin (Tg) evaluation is currently used in the follow-up of patients with differentiated thyroid carcinoma (DTC), but the measurement methods are flawed by analytical inaccuracy. In this paper we describe the results of a comparison between seven different immunoradiometric assays (IRMAs) for Tg determination.

MATERIAL AND METHODS

Tg was measured in 50 patients with DTC by means of the following commercially available IRMA kits: HTGK-2 (DiaSorin), Tg IRMA (Schering-CIS bio international), ELSA-hTG (Schering-CIS bio international), Tg IRMA C.T. (ICN Pharmaceuticals), SELco Tg (Medipan Diagnostica), Tg Bridge IRMA (Adaltis) and IRMA-mat Tg (BYK-Sangtec Diagnostica). The distribution of the Tg values measured by the different IRMAs was compared and a correlation analysis was performed.

RESULTS

The Tg values were widely dispersed and the classification of patients according to Tg concentrations of clinical relevance varied depending on the IRMA used.

CONCLUSION

Despite efforts to develop standardized Tg assays, the measurement of this biomarker is still affected by a considerable degree of analytical inaccuracy. Tg values vary widely between assays and the classification of patients according to Tg values with clinical relevance is still dependent on the assay used.