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The GBI TSH Neonatal Screening Kit is designed for the quantitative determination of Thyroid Stimulating Hormone (TSH) concentrations in neonatal blood samples that have been collected onto Whatman 903 specimen collection paper. The results are used to screen newborns for congenital hypothyroidism.

The GBI TSH Neonatal Screening Kit is an enzyme immunoassay. A highly specific polyclonal goat antihTSH (human) antibody has been immobilized onto each well of the 96-well microplates provided. To begin the assay, sample discs punched from dried whole blood spot standards, controls and neonate specimens are added to the coated wells. An elution buffer is also added. The plate is incubated to elute TSH from the sample disc and to allow capture of the eluted TSH by the antibody immobilized onto the microplate wells. Following incubation the plates are washed to remove the sample discs as well as the eluate. A second antibody, a D-specific anti-hTSH monoclonal that has been conjugated to the enzyme horseradishperoxidase (HRP), is then added to the wells and incubated. The eluted TSH of the sample already captured by the microplate-bound antibody is now also bound by the enzyme-conjugated monoclonal antibody added. An antibody-TSH-antibody bridge, or "sandwich", forms that is bound to the surface of the microplate wells. Any unbound complexes are removed with subsequent plate washings. The final stage of the assay is the detection of the microwell-bound complexes by the addition of a color developing reagent. The enzyme (HRP) portion of the bound "sandwich" reacts with the color developer, 3, 3', 5, 5'-Tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The TMB/ H2O2 liquid is converted from colorless to blue. The degree of color change is directly proportional to the amount of TSH antigen that is bound in the well. The color development is terminated with the addition of a color stopper that converts the blue to yellow. The results are measured with a microplate reader at a wavelength of 450 mm. The absorbance measured is directly proportional to the concentration of TSH in the sample. A standard curve is generated by plotting the light absorbance of each standard versus its known TSH concentrations of TSH in the unknown samples are determined by interpolation from this standard curve.