Multicenter study on TGPO autoantibody prevalence in various thyroid and non-thyroid diseases; relationships with thyroglobulin and thyroperoxidase autoantibody parameters

Objective: TGPO autoantibodies (aAbs) that bind simultaneously to thyroglob ulin (Tg) and thyroperoxidase (TPO) are present in the serum of patients wi th autoimmune thyroid diseases (AITD) and have been found to differ from mo nospecific Tg and TPO aAbs. To obtain further insights on the prevalence de fined as the rate of occurrence and significance of TGPO aAbs in a large po pulation, we carried out a collaborative study involving 15 European teams. Methods: Serum samples from 3122 patients with various thyroid and non-thyr oid diseases and normal subjects were assayed using a novel TGPO aAb detect ion kit. This test was designed so that TGPO aAbs are trapped between the T g-coated solid phase and the soluble TPO labeled with a radioiodinated mono clonal antibody. Results: Only three out of the 220 normal subjects (prevalence of 1.4%) wer e found to have positive TGPO aAb levels, which were mainly observed in the patients with AITD: the group of patients suffering from Hashimoto's thyro iditis had a TGPO aAb prevalence of 40.5% (n = 437 patients), those with Gr aves' disease, a prevalence of 34.6% (n = 645) and those with post-partum t hyroiditis, 16.0% (n = 243). Among the non-AITD patients with positive TGPO aAb levels, the TGPO aAb prevalence ranged from 20.7% among those with thy roid cancer (n = 240) to 0% among those with toxic thyroid nodules (n = 47) . Among the patients with non-thyroid diseases, the TGPO aAb prevalence ran ged from 9.8% in the case of Biermers pernicious anemia (n = 78) to 0% in t hat of premature ovarian failure (n = 44), It is worth noting that the grou ps showing the highest TGPO aAb prevalence also contained the patients with the highest TGPO aAb titers, Statistical comparisons between the TGPO aAb prevalences in the various groups showed that TGPO aAb could be used as a p arameter to distinguish between the groups of Hashimoto's and Graves' patie nts and between the women with post-partum thyroiditis and the post-partum women with only Tg and/or TPO aAb established during early pregnancy. Unexp ectedly, the correlations between TGPO aAbs and Tg and TPO aAbs were found to depend mainly on the assay kit used. Conclusion: High TGPO aAb titers are consistently associated with AITD but the reverse was not found to be true. TGPO aAbs are a potentially useful to ol, however, for establishing Hashimoto's diagnosis, and would be worth tes ting in this respect with a view to using them for routine AITD investigati ons.