Prevalence, clinical significance and prognostic value of anti-thyroglobulin antibodies in the follow-up of patients with differentiated thyroid carcinoma: a retrospective study.

AIM

Elevated persistent value of antithyroglobulin antibodies (Ab-Tg) in differentiated thyroid carcinoma (DTC) patients may interfere with Tg determination. The aim of the study was to evaluate the use of Ab-Tg as tumor marker as a replacement for thyroglobulin (Tg).

METHODS

From 1990 al 2004 767 patients have been treated and followed, mean follow-up years 6.9+/-2.4. Thirty-two patients Ab-Tg positive after radioiodine ablation, who had showed during the follow-up stable indosable value di Tg, have undergone analysis.

RESULTS

The recurrences were statistically more significant when Ab-Tg were increased, than when Ab-Tg were stable or diminished during the time (P<0.0001). Lymphocytic thyroditis was found in thirteen patients (40.6%) at histological specimen after thyroidectomy. The persistence of lymphocytic thyroditis has not modified the value of Ab-Tg as tumor marker (P<0.001). The 10/32 (31.2%) patients Tg negative have been compared to the 61/712 patients Ab-Tg positive (8.6%) who relapse. The recurrence rate was significantly higher for the first group of patients than that for the second (P<0.0001). Multivariate analisys showed N1 (P<0.001; OR 2.51) and Ab-Tg positive (P<0.001; OR: 6.15) associated with recurrences.

CONCLUSIONS

Ab-Tg must be determined, in concomitance with Tg, during the follow-up of DTC, to establish the accuracy of Tg, in order to use it as tumour marker. It must be kept in mind that the strongest indication for relapse due to Ab-Tg is an increasing of level in the same patient measured in the long time. Persistent elevated Ab-Tg levels are prognostic of future recurrences.