Recovery-test or immunoradiometric measurement of anti-thyroglobulinautoantibodies

The determination of thyroglobulin (Tg) in the follow-up of differentiated thyroid carcinomas (DTC), is routinely used in nuclear medicine, although some problems, like a disturbed recovery-test (RT) or autoantibodies to thyroglobulin (TgAb), are well known. But it is a controversial issue in literature, whether the determination of TgAb should be performed beside or instead of the RT. Objective: The study compares the clinical value of the determination of both TgAb and RT with sensitive assays. Methods: 356 patients (pts) were investigated. The results were compared to the concentration of Tg in the sera of the pts. 288 pts stayed tumor-free, the remaining 68 pts showed a recurrence (local and/or metastatic) of their DTC. We measured Tg (with RT) using an immunoradiometric assay (Tg-IRMA; SELco® Tg; Fa. Medipan Diagnostica GmbH) and TgAb using a direct assay (CentAK® anti-Tg; also from Fa. Medipan). Results: The prevalence of TgAb, and of disturbed RT respectively, in the whole population of DTC-pts was 7,6%, in the subgroup of tumor-free pts 6,6%, and in the remaining pts with tumor-recurrence 11,8%, respectively 2,0%, 1,7% and 2,9%. In a significantly higher percentage of pts with local/metastatic recurrence, both a positive TgAb (p <0,001) and a disturbed RT (p <0,05) were found. 7/68 pts with tumor-recurrence but Tg <1 ng/ml showed positive TgAb, only 2/7 had a disturbed RT. In this group, no patient with Tg >1 ng/ ml demonstrated either positive TgAb or disturbed RT (p <0,001 and p <0,05). Conclusion: The determination of TgAb in the follow-up of DTC is necessary, because it supports a suspicion to tumor-recurrence in pts with negative Tg. Also the RT is of great value because of a possibly High dose hook-effect.

[Recovery test or immunoradiometric measurement of anti-thyroglobulin autoantibodies for interpretation of thyroglobulin determination in the follow-up of different thyroid carcinoma]

The determination of thyroglobulin (Tg) in the follow-up of differentiated thyroid carcinomas (DTC), is routinely used in nuclear medicine, although some problems, like a disturbed recovery-test (RT) or autoantibodies to thyroglobulin (TgAb), are well known. But it is a controversial issue in literature, whether the determination of TgAb should be performed beside or instead of the RT.

OBJECTIVE

The study compares the clinical value of the determination of both TgAb and RT with sensitive assays.

METHODS

356 patients (pts) were investigated. The results were compared to the concentration of Tg in the sera of the pts. 288 pts stayed tumor-free, the remaining 68 pts showed a recurrence (local and/or metastatic) of their DTC. We measured Tg (with RT) using an immunoradiometric assay (Tg-IRMA; SELco Tg; Fa. Medipan Diagnostica GmbH) and TgAb using a direct assay (CentAK anti-Tg; also from Fa. Medipan).

RESULTS

The prevalence of TgAb, and of disturbed RT respectively, in the whole population of DTC-pts was 7.6%, in the subgroup of tumor-free pts 6.6%, and in the remaining pts with tumor-recurrence 11.8%, respectively 2.0%, 1.7% and 2.9%. In a significantly higher percentage of pts with local/metastatic recurrence, both a positive TgAb (p < 0.001) and a disturbed RT (p < 0.05) were found. 7/68 pts with tumor-recurrence but Tg < 1 ng/ml showed positive TgAb, only 2/7 had a disturbed RT. In this group, no patient with Tg > 1 ng/ml demonstrated either positive TgAb or disturbed RT (p < 0.001 and p < 0.05).

CONCLUSION

The determination of TgAb in the follow-up of DTC is necessary, because it supports a suspicion to tumor-recurrence in pts with negative Tg. Also the RT is of great value because of a possibly High dose hook-effect.