Improved prediction of relapse of Graves' thyrotoxicosis by combined determination of TSH receptor and thyroperoxidase antibodies.

BACKGROUND: Recently, we and others have demonstrated that high levels of auto-antibodies to the human TSH-receptor (TRAb) predict relapse of hyperthyroidism in Graves' disease (GD). Our objective was to extend the outcome of the prediction by combining TRAb with thyroperoxidase antibody (TPO-Ab) measurement. PATIENTS AND METHODS: One hundred and thirty-one GD patients (118 females, 13 males) were analysed, of whom 94 patients (71.8%) had relapse, whereas 37 (28.2%) went into remission. Second generation TRAb and TPO-Ab assays were performed in GD patients with relapse and remission in mean 4.3 months after initial diagnosis.
RESULTS: The mean anti-TPO-Ab levels were similar in all patients with relapse and remission. However, there was a steady decline from 4047 U/ml to 530 U/ml in the remission group that correlated positively with TRAb values (>2 to >10 IU/l). The relapse group remained at consistently high levels. The positive predictive value (PPV) for relapse in patients with TRAbs >6 IU/l and anti-TPO-Abs >5000 U/ml was 100, whereas TRAbs >6 IU/l and anti-TPO-Abs >500 U/ml were associated with a PPV of 93.7 up to 96 (p=0.008). These Ab constellations accounted for about one third of all GD patients. For patients with TRAbs between >2 and <6 IU/l the PPV was 66.7-90.0.
CONCLUSION: Our follow-up analysis indicates that the prediction of relapse of GD can be improved by a combined measurement of TRAb and TPO-Ab. In patients with moderately increased Abs, determined about 6 months after initial diagnosis, an ablative therapy can be approached without delay.