Concordance of eight kits for antithyroid peroxidase autoantibodies determination

Numerous methods are proposed to quantify antithyroid peroxidase autoantibo dies. No standardization exists but most assays use the standard MRC 66/387 with a calibration factor. Costs of the tests vary between the different k its. We evaluated the concordance of eight peroxidase autoantibodies assay kits in two centres, using a panel of sera from 269 subjects: controls (n = 100), patients with autoimmune thyroid disease (n = 77; Graves' disease, H ashimoto's thyroiditis), patients with non-autoimmune thyroid disease (n = 69; nodular goiter, differentiated thyroid carcinoma) and individual sera w ith thyroglobulin antibodies only (n = 23). The concordance between the eig ht methods was high, ranging from 88.3% to 98.8% with the total panel of se ra. The majority of assays demonstrated high diagnostic performance. We enc ountered some false-positive results at borderline positive levels, and the nonrecognition of some sera by competitive assays.