THYROPEROXYDASE ANTIBODY-ASSAY IN COMMON THYROID PATHOLOGY - CLINICALAND METHODOLOGICAL APPROACH

Thyroid peroxydase antibody levels were measured in 409 patients who c ame to the thyroid pathology consultation of our Institution between S eptember, 1990, and November, 1991, and were compared with a reference population. In the first 231 patients, we compared the results obtain ed 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-TPO(R) >>, Henning, Germany) beca use 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 m ade in patients examined during the thyroid pathology consultation, 13 7 (33.5 %) had pathological values ranging from 100 to 5000 U/ml and e ven more. Peroxydase antibodies are mainly found in patients with prim ary hypothyroidism (positive in 82 % of cases) and graves' hyperthyroi dism (positive in 81 %). We have also observed the highest levels in t hese two conditions. In addition, we have demonstrated a group of pati ents with normal thyroid conditions who were positive for peroxydase A ntibodies, sometimes in a family with a history of thyroid pathology. These may be at higher risks to develop hypothyroidism in the future t han the general population. A TRH test in some subjects and the clinic al evolution of these patients lead us to advocating TPO antibody assa y for screening on the first consultation. Endocrine surveillance is a dvisable in case of positive results.