Large discrepancy in the results of sensitive measurements of thyroglobulin antibodies in the follow-up on thyroid cancer: a diagnostic dilemma.
During follow-up on patients treated for differentiated thyroid cancer, thyroglobulin (Tg) antibodies can interfere with the Tg assay, making the use of Tg less reliable as a tumor marker.


OBJECTIVE
To compare Tg and Tg autoantibodies (Tg-Ab) methods used in Denmark, regarding the number of patient samples being accepted for evaluating the result of a serum thyroglobulin (s-Tg) measurement.


METHODS
95 consecutive blood samples drawn from patients in 2006 in one center were selected according to the following criteria: s-Tg <1μg/l and accepted BRAHMS Tg+ recovery test using 50 ng of Tg. Samples were retested with: (1) DPC IMMULITE 2000 Tg and Tg-Ab, (2) BRAHMS Tg and Tg-Ab on Kryptor, (3) BRAHMS Tg+ and Dynotest anti-Tg, (4) DELFIA hTg and recovery test using 25 ng of Tg, and (5) BRAHMS Tg+ with recovery test using 1 and 50 ng of Tg.


RESULTS
The number of patient samples that was not accepted for Tg evaluation varied from 2 to 26% when the reference values suggested by the manufacturers of the assay were used. When using the detection limit to the cutoff seen in epidemiological studies the number increased to 40%.


CONCLUSIONS
We found large discrepancies in acceptance of patient samples for s-Tg evaluation, thus illustrating a diagnostic dilemma.
Department of Endocrinology, Herlev Hospital, Copenhagen, Denmark.
Birte
B
Nygaard
Department of Oncology, Herlev Hospital, Copenhagen, Denmark.
Jens
J
Bentzen
Department of Endocrinology, Aalborg Hospital, Aalborg, Denmark.
Peter
P
Laurberg
Department of Biochemistry, Odense University Hospital, Odense, Aarhus, Denmark.
Susanne Møller
SM
Pedersen
Department of Oncology, Odense University Hospital, Odense, Aarhus, Denmark.
Lars
L
Bastholt
Department of Biochemistry, Aarhus Hospital, Aarhus, Denmark.
Aase
A
Handberg
Department of Oncology, Aarhus Hospital, Aarhus, Denmark.
Carsten
C
Rytter
Department of ENT Head and Neck Surgery, Odense University Hospital, Odense, Aarhus, Denmark.
Christian
C
Godballe
Department of Endocrinology, Herlev Hospital, Copenhagen, Denmark.
Jens
J
Faber
Thyroglobulin; Thyroglobulin antibodies; Thyroid cancer