[Evaluation of the diagnostic power of 3 methods for assaying free T4. Results in the diagnostic strategy of hyperthyroidism]. / Evaluation de la puissance diagnostique de trois méthodes de dosage de la T4 libre. Conséquence sur la stratégie diagnostique de l'hyperthyroïdie.

The free thyroxin (FT4) tests of Amersham, Clinical Assay and Corning Medical were evaluated in 240 patients who were suspected of hyperthyroidism. The diagnostic performances of the Corning method were of less value while those of the other methods were equivalent to that obtained with the free thyroxin index for an average cost reduced. Furthermore our results show that T3 determination is better than T4 determination in patients who remained doubtful after FT4. However the development of ultra-short methods of measurement of total thyroid hormone blood levels using fluorescence polarization could lead to reconsider the diagnostic strategy of hyperthyroidism.