TY - JOUR
T1 - Clinical assessment of a radioimmunoassay for free thyroxine using a modified tracer
AU - Chan, D. W.
AU - Waud, J. M.
AU - Hsu, T. H.
PY - 1983
Y1 - 1983
N2 - A radioimmunoassay for measuring free thyroxine in plasma was introduced by Amersham using a I-125-labeled T4 derivative that does not bind significantly to the thyroxine-binding proteins. We evaluated this RIA for its clinical utility in assessing 278 patients with thyroid and nonthyroidal diseases. The precision of the Amerlex free T4 assay, expressed as coefficient of variation, was 20% at 0.16 ng/dl, 6.9% at 0.55 ng/dl, 4.2% at 1.08 ng/dl, 5.3% at 2.29 mg/dl, and 6.3% at 3.18 ng/dl. A reference range for free T4 was established as 0.68-1.8 ng/dl, n = 171. The correlation coefficients (r) of a dialysis method and a free thyroxine index were 0.871 and 0.911, respectively. Free T4 correctly classified 98% euthyroid, 92% hypothyroid, 100% hyperthyroid, 100% euthyroid with elevated TBG, and 87% of phenytoin patients. In addition, 80 patients with acute nonthyroidal illness were studied. Most of these patients have normal to low free T4, very low T3, and elevated rT3. We found this free T4 assay to be precise, easy to perform, and reliable in classifying thyroid status in most patients.
AB - A radioimmunoassay for measuring free thyroxine in plasma was introduced by Amersham using a I-125-labeled T4 derivative that does not bind significantly to the thyroxine-binding proteins. We evaluated this RIA for its clinical utility in assessing 278 patients with thyroid and nonthyroidal diseases. The precision of the Amerlex free T4 assay, expressed as coefficient of variation, was 20% at 0.16 ng/dl, 6.9% at 0.55 ng/dl, 4.2% at 1.08 ng/dl, 5.3% at 2.29 mg/dl, and 6.3% at 3.18 ng/dl. A reference range for free T4 was established as 0.68-1.8 ng/dl, n = 171. The correlation coefficients (r) of a dialysis method and a free thyroxine index were 0.871 and 0.911, respectively. Free T4 correctly classified 98% euthyroid, 92% hypothyroid, 100% hyperthyroid, 100% euthyroid with elevated TBG, and 87% of phenytoin patients. In addition, 80 patients with acute nonthyroidal illness were studied. Most of these patients have normal to low free T4, very low T3, and elevated rT3. We found this free T4 assay to be precise, easy to perform, and reliable in classifying thyroid status in most patients.
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M3 - Article
C2 - 6854399
AN - SCOPUS:0020955504
SN - 0161-5505
VL - 24
SP - 498
EP - 504
JO - Journal of Nuclear Medicine
JF - Journal of Nuclear Medicine
IS - 6
ER -