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. Purpose: 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. Design: 95 consecutive
blood samples drawn from patients in 2006 in one
center were selected according to the following criteria:
s-Tg ! 1g/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%. Conclusion: We found large discrepancies
in acceptance of patient samples for s-Tg evaluation,
thus illustrating a diagnostic dilemma.