TSH, ELISA

The principle of the following enzyme immunoassay test follows a typical one-step capture or ‘sandwich’ type assay.

The assay makes use of two highly specific monoclonal antibodies: A monoclonal antibody specific for TSH is immobilized onto the microwell plate and another monoclonal antibody specific for a different region of TSH is conjugated to horse radish peroxidase (HRP).

TSH from the sample and calibrators are allowed to bind simultaneously to the plate and to the HRP conjugate. The washing and decanting steps remove any unbound HRP conjugate.

After the washing step, the enzyme substrate is added. The enzymatic reaction is terminated by addition of the stopping solution. The absorbance is measured on a microtiter plate reader. The intensity of the colour formed by the enzymatic reaction is directly proportional to the concentration of TSH in the sample.

A set of calibrators is used to plot a calibration curve from which the amount of TSH in patient samples and controls can be directly read.