[Determination of total serum triiodothyronine in hyperthyroidism: comparison of fluorescence polarization and immunoenzymology].

We evaluated the performances of the Abbott fluorescence polarization assay (FPIA) utilizing the TDx system for human total triiodothyronine (T3) in hyperthyroidism. We compared the results with an immunoenzymometric assay (IEA) (Enzymum Test T3 Boehringer-Mannheim). Greatest attention was focused on the diagnosis of hyperthyroidism because detection of subclinical hyperthyroidism is important. The repeatability of the Abbott fluorescence polarization assay was satisfying (m = 8.07 +/- 0.37 nmol.l-1, CV = 4.59%). The reproducibility was tested with Abbott control sera: m = 4.58 +/- 0.53 nmol.l-1 and CV = 11.5 per cent for level M; m = 7.95 +/- 0.66 nmol.l-1 and CV = 8.23 per cent for level H; m = 2.38 +/- 0.39 nmol.l-1 and CV = 16.5 for level L. The correlation of results of the Abbott assay with those of the Boehringer assay was good for samples from hyperthyroid patients. Values for hyperthyroid and euthyroid subjects were resolved slightly better with the Abbott FPIA than with Boehringer IEA. The Abbott total T3 fluorescence polarization assay may have an additional role to play in monitoring thyroid function in patients under iodine treatment (amiodarone) to eliminate a secondary hyperthyroïdism.