We describe two siblings with artefactually increased results for free thyroxin in serum as measured with the Amerlex analog method, despite normal thyroxin transport. The cause of the artefact is identified as a variant albumin with enhanced affinity for the Amerlex thyroxin-analog.

A double-antibody enzyme immunoassay was developed for determination of thyroxin-binding globulin in dried blood samples on filter paper. The measurable concentration range of thyroxin-binding globulin in two 3-mm blood discs was 3.3 to 52 mg/L equivalent of serum (i.e., equivalent to the concentrations in known serum standards). Thyroxin-binding globulin in dried blood samples on filter paper ...

We have investigated the clinical utility of two direct radioimmunoassays for free thyroxin, an enzyme-inhibition immunoassay, and a direct measurement of thyroxin-binding globulin (TBG) by radioassay. All assay methods correctly identified greater than or equal to 90% of euthyroid, hyperthyroid, and hypothyroid patients who had normal TBG concentrations. In patients with altered TBG concentrat...

Serum free thyroxin (FT4) in normal nonpregnant and pregnant subjects was measured by radioimmunoassay (RIA) with Amerlex FT4 RIA (Amersham International) and LiquiSol FT4 RIA (Damon Diagnostics) kits. Amerlex FT4 values in serum from pregnant women were lower than those in serum from nonpregnant women, but LiquiSol FT4 values were similar in serum from both groups. Amerlex FT4 values were dire...

This enzyme immunoassay for free thyroxin (FT4) involves simultaneous incubation of sample and thyroxin conjugated to horseradish peroxidase (EC 1.11.1.7) in antibody-coated tubes at room temperature. The test can be performed in 90 min. It is not influenced by variations in concentrations of thyroxin-binding globulin (TBG), thyroxin-binding prealbumin, or albumin. With increased concentrations...

Serum thyroxin was nearly or completely undetectable by radioimmunoassay in an elderly patient with Graves' disease being treated with methimazole. Abnormal binding of thyroxin to antibodies of the IgG variety was shown, the association constant of the complex being 8.0 x 10(8) L/mol and the binding capacity 6.3 nmol/g of IgG. The effect of the antibody on results of radioimmunoassay of free th...

I examined the effect of albumin deficiency, as might occur in pregnancy and nonthyroidal illness, on four analog-based assays for free thyroxin (Amersham's Amerlex, Diagnostic Products Corporation's Coat-A-Count "one-step," Clinical Assays' Gammacoat "one-step," and Corning's Immophase "single-step"). In subjects with albumin deficiency per se, Amerlex and Coat-A-Count results for free thyroxi...

The influence of a highly diluted agitated, i.e. homeopathically prepared thyroxin solution (10(-30), final concentration in the basin water 10(-35) parts by weight after the first application) on metamorphosis in lowland Rana temporaria from the spawn stage on was studied. The treatment with homeopathically prepared thyroxin solution (10(-30)) starts at the frogspawn stage. It represents a too...

We describe a rapid, simple nonseparation fluoroimmunoassay for determination of thyroxin in serum. The assay is based on the labeling of thyroxin directly with a fluorescent europium chelate, the fluorescence of which is quenched on binding to an antithyroxin antibody. With the assay buffer we used, maximum quenching is 90%. The rapid achievement of equilibrium in the assay solution, regardles...