- CAN:
- EU:
- USA: For Research Use Only. Not For Use In Diagnostic Procedures.
The Free T3 ELISA is a competitive immunoassay. Competition occurs between Free T3 present in calibrators, controls, specimen samples and an enzyme-labelled antigen (HRP conjugate) for a limited number of anti- T3 antibody binding sites on the microplate wells. After a washing step that removes unbound materials, the TMB substrate (enzyme substrate) is added which reacts with HRP to form a blue-coloured product that is inversely proportional to the amount of Free T3 present. Following an incubation, the enzymatic reaction is terminated by the addition of the stopping solution, converting the colour from blue to yellow. The absorbance is measured on a microplate reader at 450 nm. A set of calibrators is used to plot a calibrator curve from which the amount of Free T3 in specimen samples and controls can be directly read.
The labelled T3 (HRP conjugate) employed in this assay system has shown no substantial binding properties towards thyroxine binding globulin (TBG) or 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 T3 and its carrying proteins. The assay is carried out under normal physiological conditions of pH, temperature and ionic strength.