Clinical assessment of a radioimmunoassay for free thyroxine using a modified tracer

Journal Article · Wed Jun 01 04:00:00 EDT 1983 · J. Nucl. Med.; (United States)

OSTI ID:5394157

Chan, D W; Waud, J M; Hsu, T H

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 ng/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.

• Research Organization: Johns Hopkins University and Hospital, Baltimore, Maryland
• OSTI ID: 5394157
• Journal Information: J. Nucl. Med.; (United States), Journal Name: J. Nucl. Med.; (United States) Vol. 24:6; ISSN JNMEA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CARBOXYLIC ACIDS
DAYS LIVING RADIOISOTOPES
DIAGNOSIS
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE DISEASES
ENDOCRINE GLANDS
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MAN
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
PRIMATES
RADIOASSAY
RADIOIMMUNOASSAY
RADIOISOTOPES
THYROID
THYROID HORMONES
THYROXINE
TRACER TECHNIQUES
VERTEBRATES