[Analytical evaluation of third generation TSH assay. Application to the exploration of thyrotropin suppression in differentiated thyroid cancer].
Intravenous TRH (200 micrograms Protiréline) injection was performed in 137 patients who had undergone thyroidectomy for differentiated thyroid carcinoma and treated by a suppressive thyroid therapy. Serum thyroid stimulating hormone (TSH) was measured before and 30 minutes after the injection. 143 tests were performed. The TSH method used was a chemiluminometric assay (Chiron Diagnostics). We study the analytical characteristics of the method. The limit of detection was 0.003 mUI/l. Interassay precision showed a functional sensitivity of 0.015 m UI/l with 20% interassay CV in agreement with the third generation criterion. There was a good correlation between TSH values at T0 and T30 minutes. In 143 tests, 40 (28%) showed a basal TSH value less than 0.003 mUI/l; delta TSH (TSH at T30-TSH at T0) was less than 0.015 mUI/l in about 68% of the cases and less than 0.031 mUI/l for the others. In 20% of the tests (29) TSH T0 were between 0.003 and 0.015 mUI/l and delta TSH less than 0.204 mUI/l. Finally the 74 remaining tests with a basal TSH value higher than the functional sensitivity of the method showed delta TSH less than 0.4 mUI/l if the TSH T0 was less than 0.05 mUI/l. The delta TSH remained less than 0.6 mUI/l if the TSH T0 was less than 0.1 mUI/l. Inversely, if TSH T0 was higher than 0.1 mUI/l delta TSH could be higher than 1.0 mUI/l. Third generation TSH assay allows us to abandon TRH test for the follow-up of thyroidectomized patients with suppressive thyroid hormonotherapy in so far as TSH assay is well established. We conclude that a basal TSH less than the functional sensitivity (0.015 mUI/l) can predict a TSH response to TRH stimulation test less than 0.2 mUI/l.
Charrié
A
A
Laboratoire de Médecine Nucléaire, Hôpital de l'Antiquaille, Lyon.
Mesnard
X
X
Tourniaire
J
J
D005260:Female; D006801:Humans; D007118:Immunoassay; D007700:Kinetics; D008163:Luminescent Measurements; D008297:Male; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000097:blood* / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone
D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin
Evaluation analytique d'un dosage de TSH de troisième génération. Application à l'exploration du freinage thyréotrope des cancers thyroïdiens différenciés.