Free Thyroxine (fT4) LIA Assay Kit


The Free Thyroxine (fT4) LIA Assay Kit is for the direct quantitative determination of free thyroxine in human serum by a chemiluminescence immunoassay (LIA). The Eagle Biosciences Free Thyroxine (fT4) LIA assay kit is for research use only and not to be used in diagnostic procedures.

SKU: T4F31-L01 Categories: , ,

Free Thyroxine (fT4) LIA Assay Kit

Free Thyroxine (fT4) LIA Assay Kit is For Research Use Only

Size: 1×96 wells
Sensitivity: 1 pg/mL
Dynamic Range: 2–80 pg/mL
Incubation Time: 90 minutes
Sample Type: Serum
Sample Size: 25 μL
Controls Included

Assay Principle for Free Thyroxine (fT4) LIA Assay Kit

The principle of the Free Thyroxine (fT4) LIA Assay Kit is a chemiluminescence immunoassay (LIA) test that follows the typical competitive binding scenario. Competition occurs between an unlabelled antigen (present in standards, control and patient samples) and an enzyme-labelled antigen (conjugate) for a limited number of antibody binding sites on the microplate. The washing and decanting procedures remove unbound materials. After the washing step, the luminescence substrate solution is added. The relative luminescence units (RLUs) are measured on a microtiter plate luminometer. The RLU values are inversely proportional to the concentration of fT4 in the sample. A set of calibrators are used to plot a standard curve from which the amount of fT4 in patient samples and controls can be directly read. The labelled T4 (conjugate) employed in this assay system has shown no binding properties towards thyroxine-binding globulin (TBG) and human serum albumin (HSA). The binding sites on the microplates are designed to be of a low binding-capacity in order not to disturb the equilibrium between T4 and its carrying proteins. The assay is carried out under normal physiological conditions of pH, temperature and ionic strength.

Approximately 0.2 mL of serum is required per duplicate determination. Collect 4–5 mL of blood into an appropriately labelled tube and allow it to clot. Centrifuge and carefully remove the serum layer. Store at 4°C for up to 24 hours or at -10°C or lower if the analyses are to be done at a later date. Consider all human specimens as possible biohazardous materials and take appropriate precautions when handling.

Related Products

Thyroxine (T4) ELISA Assay Kit
Free Thyroxine (fT4) ELISA
Free Testosterone LIA Assay

Additional Information

Assay Background

Thyroxine (T4), the principal thyroid hormone, circulates in blood almost completely bound to carrier proteins. However, only the free (unbound) fraction of thyroxine is considered to be biologically active. The main carriers of thyroxine are thyroxine-binding globulin (TBG), pre-albumin and albumin. The measurement of free thyroxine (fT4) levels correlate better with the clinical status than total thyroxine levels. The free T4 assay is a one step competitive LIA system that is rapid and easy to perform compared to equilibrium dialysis and ultrafiltration methods, which are cumbersome and time-consuming. This system employs a highly specific monoclonal antibody and a non-analog tracer that was proved experimentally to have no significant binding to TBG and albumin. In the euthyroid, normal population the free T4 concentration is 7–22 pg/mL. The level of free T4 is decreased in hypothyroidism while in thyrotoxic patients the level of free T4 is increased.

Package Inserts


Please note: All documents above are for reference use only and should not be used in place of the documents included with this physical product. If digital copies are needed, please contact us.

Product Citations