Witherspoon L R, Shuler S E, Gilbert S S
J Nucl Med. 1984 Feb;25(2):188-96.
We have examined the performance of a commercial free-thyroxine assay in which a radiolabeled T4 derivative permits the competitive quantitation of extracted T4 in the presence of serum proteins. After the total T4 pool had been radiolabeled with either I-125 T4 or I-131 T4, the solid-phase antibody was found to be associated with 4-8% of the total T4 present in the assay tube. Of this, 15-60% was displaceable (antibody-bound). The assay estimated free T4 to be 0.6-1.8 ng/dl in euthyroid patients, and distinguished them from hyperthyroid (sensitivity 91%) and hypothyroid patients (sensitivity 91%) without apparent TBG dependence. In patients with severe nonthyroidal illnesses, the assay correctly quantitated a reduced extracted mass in some. In other patients, however, the assay results were inappropriately lower than the actual extracted mass, in agreement with the FTI but not with the measurements of free T4 by dialysis. This assay appears to produce clinically appropriate results in most patients. In some nonthyroidally ill patients however, the indicated free T4 is spuriously low.
我们检测了一种商业化游离甲状腺素测定法的性能，该方法中一种放射性标记的T4衍生物可在血清蛋白存在的情况下对提取的T4进行竞争性定量。在用I-125 T4或I-131 T4对总T4库进行放射性标记后，发现固相抗体与测定管中存在的总T4的4-8%相关。其中，15-60%是可置换的（抗体结合的）。该测定法估计甲状腺功能正常患者的游离T4为0.6-1.8 ng/dl，并能将他们与甲状腺功能亢进患者（敏感性91%）和甲状腺功能减退患者（敏感性91%）区分开来，且无明显的甲状腺素结合球蛋白（TBG）依赖性。在患有严重非甲状腺疾病的患者中，该测定法在一些患者中正确地定量了降低的提取量。然而，在其他患者中，测定结果比实际提取量不适当地低，这与游离甲状腺素指数（FTI）一致，但与通过透析测定的游离T4结果不一致。该测定法在大多数患者中似乎能产生临床上合适的结果。然而，在一些患有非甲状腺疾病的患者中，所示的游离T4假性偏低。
