Clinical Evaluation of a New Highly Sensitive Thyroglobulin Assay in Differentiated Thyroid Carcinoma
Clinical Evaluation of a New Highly Sensitive Thyroglobulin Assay in Differentiated Thyroid Carcinoma
Human thyroglobulin (Tg) is the most sensitive biochemical marker for recurrence of
 differentiated cancer (DTC), especially after the complete removal of thyroid tissue through
 surgery and radioiodine therapy (RIT).

 Unfortunately, current assays for measuring Tg in blood samples are not sensitive enough to
 reliably measure Tg while patients are under thyroid hormone replacement therapy. Instead
 patients have to withdraw thyroid hormone for several weeks or receive costly injections of
 recombinant thyroid stimulating hormone (TSH) in order to raise Tg production by thyroid
 remnant and/or thyroid cancer cells so that it can be measured by current Tg assays. Other
 patients have antibodies against Tg that interfere in current immunoassays.

 The purpose of the study was to characterize a new highly sensitive assay for measuring Tg in
 the serum in thyroid cancer patients both on thyroid hormone therapy and off therapy in
 comparison to the normal routine assay already in use at Münster University Hospital.
Sera of 100 consecutive DTC patients after total thyroidectomy were to be collected at the
 Department of Nuclear Medicine both under TSH-suppression therapy and under endogenous TSH
 stimulation (TSH > 25 mU/l). All patients were staged by clinical examination, cervical
 ultrasound (7.5 MHz), I-131 whole-body scintigraphy and - where applicable - F18-FDG-PET.
 Written informed consent was obtained from all pts. Sera were taken in separation tubes
 without anticoagulants and stored at -20°C until analysis. Sera were allowed to come to room
 temperature prior to analysis.

 Tg, TgR and TgAb concentrations were determined by fully automated two-site chemiluminescence
 immunoassays (CLIA; Nichols Advantage®; Nichols Institute Diagnostics, San Clemente,
 California). All 3 assays are based on the identical highly purified hTg material for
 calibration (Tg), recovery (TgR) and antigen (TgAb; biotinylated and acridinium ester
 labeled) for optimum comparability of test results.

 In addition, Tg and TgR was measured by a fully automated two-site TRACE immunoassay (BRAHMS
 Kryptor®, Brahms AG, Hennigsdorf, Germany) and TSH with a 3rd-generation CLIA assay (TSH-3,
 Advia Centaur, Bayer Corporation).
Inclusion Criteria:

 -  histological diagnosis of differentiated thyroid carcinoma

 -  total or near total thyroidectomy

 -  informed consent

 Exclusion Criteria:

 -  no informed consent