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Abstract
An original radioimmunoassay for quantitation of circulating autoantibodies (aAb) to thyroperoxidase (TPO) proved to be well suited for large scale routine testing. The present study was aimed to assess the prevalence of aAb to TPO in patients with various thyroid and autoimmune diseases and, for comparison, in women referred for reproductive disorders and indication of in vitro fertilization.
Anti-TPO aAb were measured in sera from 32 healthy subjects and 262 patients thoroughly investigated for thyroid dysfunction. As determined in healthy subjects, the normal level of aAb to TPO in serum ranged from 0. 30 to 3. 07 mg/1 (of affinity-purified) anti-TPO aAb. Anti-TPO and anti-MIC aAb levels were both normal in 115 patients and correlated well (r = 0. 835, P < 0. 001) in the remaining 147 patients. Coexistence of normal level of anti-TPO aAb and abnormal level of anti-MIC aAb was found in 4 patients and ascribed to a lack of specificity or sensitivity of the test for anti-MIC aAb. Coexistence of abnormal level of anti-TPO aAb and normal level of anti-MIC aAb was found in 67 patients of whom 62 presented only slightly elevated (3. 1 to 10. 0 mg/1) anti-TPO aAb concentration; the 5 remaining patients, all with overt thyroid autoimmune disease, showed anti-TPO levels between 10. 7 to 100. 7 mg/1. In the 84 patients with established thyroid dysfunction, the prevalence of aAb to TPO (88. 1%) was higher than that observed for anti-MIC aAb (70. 2%) and did not significantly differ among patients with autoimmune thyroid disease (Graves' disease, n = 34; Hashimoto's thyroiditis, n = 24) and the 26 patients referred for various diseases (nodular goiter, n = 3; non-thyroid autoimmune disease, n = 2l; reproductive disease, n = 2). In the absence of thyroid dysfunction, the prevalence of abnormal anti-TPO aAb level ranged from 55. 0% in patients with diffuse or nodular goiter (n = 40), 33. 3% in patients with organ-specific autoimmune disease (n = 54) and 51. 0% in patients with non-organ-specific autoimmune disease (n = 49), whereas anti-MIC aAb were found in only 15. 0, 12. 9 and 4. 2% of the patients, respectively. In contrast, the women referred for reproductive disease and without thyroid and autoimmune disorders (n = 35) showed the same low prevalence (11. 4%) of aAb to TPO and the microsomal antigen.
These data demonstrated that anti-TPO/MIC aAb are more frequently detected using the new specific and sensitive assay than the common passive hemagglutination test in patients with thyroid and/or autoimmune diseases. Anti-TPO aAb testing would thus appear of help in the diagnosis of autoimmune diseases and serve to anticipate thyroid disorder in patients with autoimmune disease.