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ACE T Uptake Reagent is used in the diagnosis and treatment of thyroid disorders. It is intended for the quantitative determination of unsaturated binding sites on the thyroid-binding proteins in serum using the ACE clinical chemistry analyzer.

The ACE T Uptake Regent contains two reagents, and Antibody/Substrate reagent and an Enzyme The assay uses a mixture of enzyme glucose-6-phosphate dehydrogenase Conjugate reagent. conjugated thyroxine (G6PD-T4) and a known amount of exogeneous T4 which is allowed to bind to the thyroxine-binding proteins in the sample. A sample with increased levels of unsaturated thyroxine-binding sites, the exogeneous T4 will bind leaving G6PD-T4 conjugate free. On addition of an anti-thyroxine antibody, the G6PD-T4 conjugate is bound by the antibody and the enzyme activity is inhibited. Conversely, a sample with decreased levels of unsaturated thyroxine-binding sites will leave most exogeneous T4 unbound. Upon addition of anti-T4 antibody, the unbound exogeneous T4 will inhibit the anti-T4 binding to G6PD-T4 conjugate and produce a high G6PD enzyme activity. This phenomenon creates a relationship between unsaturated thyroxine-binding sites concentration (T Uptake) and the enzyme activity. The enzyme G6PD activity is determined bichromatically on the ACE® at 340/505 nm by measuring its ability to convert NAD* to NADH.

The Measurement of the Total Amount of Binding Sites Available for the Thyroid Hormones in Human Serum or Plasma by a Microplate Enzyme Immunossay. Measurements obtained from this device are used in the diagnosis and treatment of thyroid diseases.

The Monobind microplate EIA utilizes limited amount of anti-thyroxine antibody coated on the surface of plastic wells of a microtiter plate. Specimens, calibrators or controls are then added followed by the enzyme-T4 conjugate and thyroxine. The amount of enzyme only gets to the specimen increases. After the completion of the incubation period, the enzyme-T4 conjugate on the well is quantitated by reaction with suitable substrate. The activity of the enzyme is inversely proportional to the amount of unsaturated thyroid hormone binding sites in the specimen. The employment of several serum references of known unsaturated thyroid hormone binding capacity permits construction of a graph of absorbance and concentration. From comparison to the dose response curve, an unknown specimen's absorbance can be correlated with thyroid hormone binding capacity.

For the assessment of unsaturated thyroid binding proteins in serum or plasma using the Chiron Diagnostics ACS:180® Automated Chemiluminescence Systems.

The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are bound primarily to thyroxine-binding globulin (TBG) and to a lesser extent thyroxine-binding prealbumin (TBPA) and albumin. The ACS:180 T Uptake assay measures the number of unoccupied binding sites on these proteins and is an indirect indicator of thyroid status. T Uptake (TU) and total T4 are used to estimate the amount of circulating free T4. The estimate, or the Free Thyroxine Index (FTI), is a normalized measurement that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins, which can occur in many different physical conditions. Drugs or physical conditions that alter the patient's TBG levels or drugs that compete with endogenous T4 and T3 for protein-binding sites alter T Uptake results. When serum contains high levels of T3 or T4, as in hyperthyroidism, fewer unoccupied binding sites are available. Conversely, in hypothyroidism, more binding sites are available. The Chiron Diagnostics ACS:180 TUp assay is a double antibody competitive immunoassay using, chemiluminescent technology. The sample is incubated with Lite Reagent, which is composed of acridinium ester-labeled T3-BGG (bovine gamma globulin) and unlabeled T3. The unlabeled T3 in the Lite Reagent fills available thyroid-binding sites in the sample. The acridinium ester-labeled T3-BGG does not bind to the binding proteins in the sample. The acridinium ester-labeled T3-BGG and unlabeled T3 compete for monoclonal mouse anti-T3 antibody in the Solid Phase. The monoclonal mouse anti-T3 antibody is bound to goat anti-mouse antibody, which is covalently coupled to paramagnetic particles in the Solid Phase. A greater amount of unlabeled T3 binding to the binding proteins in the sample results in more T3-BGG-acridinium ester binding to the monoclonal antibody, an indication of a higher amount of unsaturated binding proteins.

Immunoassay for the in vitro quantitative determination of thyroxine-binding capacity in human serum and plasma.

The Elecsys® test principle is based on competition principle. Total duration of assay: 18 minutes (37° C). • 1st incubation (9 minutes): Sample (15 $\mu$ L), exogenous T4, and biotinylated T4-polyhapten (75 $\mu$ L). •2nd incubation (9 minutes): After addition of a specific anti-T4 antibody labeled with a ruthenium complex (75 $\mu$ L), the polyhapten and the antibody derivative react to form a complex, the concentration of which is inversely proportional to the concentration of the excess, exogenous T4. This immunological complex is bound to the added streptavidin-coated microparticles (35 $\mu$ L) via the interaction of biotin and streptavidin. ·The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier (0.4 second read frame). ·Results are determined via a calibration curve which is instrumentspecifically generated by 2-point calibration and a master curve provided via the reagent bar code.