[Determination of thyroid peroxidase antibodies in common thyroid pathology. Methodological and clinical approach]

Thyroid peroxidase antibody levels were measured in 409 patients who came to the thyroid pathology consultation of our Institution between September, 1990, and November, 1991, and were compared with a reference population. In the first 231 patients, we compared the results obtained with two commercial kits. The correlation coefficient between both populations of results was assessed to be 0.919. Only one of the kits was selected later ("Immutest anti-TPOR", Henning, Germany) because normal and pathological values overlapped to a lesser extent. In a population of controls (reference population). 4 cases out of 82 (4.8%) had values exceeding 100 U/ml (arbitrary units), this value being regarded as the boundary of normal conditions. Out of the 409 assays made in patients examined during the thyroid pathology consultation, 137 (33.5%) had pathological values ranging from 100 to 5000 U/ml and even more. Peroxidase antibodies are mainly found in patients with primary hypothyroidism (positive in 82% of cases) and graves' hyperthyroidism (positive in 81%). We have also observed the highest levels in these two conditions. In addition, we have demonstrated a group of patients with normal thyroid conditions who were positive for peroxidase antibodies, sometimes in a family with a history of thyroid pathology. These may be at higher risks to develop hypothyroidism in the future than the general population. A TRH test in some subjects and the clinical evolution of these patients lead us to advocating TPO antibody assay for screening on the first consultation. Endocrine surveillance is advisable in case of positive results.