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Unit Code 8724:
T4 (Thyroxine), Total Only, Serum

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Method Description

The instrument used is a Beckman Coulter DXI 800. The Access

Total T4 assay is competitive-binding immunoenzymatic assay.

A sample is added to a reaction vessel with antithyroxine antibody,

thyroxine-alkaline phosphatase conjugate, and para-magnetic

particles coated with goat antimouse capture antibody and a

stripping agent to dissociate all T4 from binding proteins. Thyroxine

in the sample competes with the thyroxine-alkaline phosphatase

conjugate for binding sites on a limited amount of specific antithyroxine

antibody. Resulting antigen: antibody complexes bind to the capture

antibody on the solid phase. After incubation in a reaction vessel,

materials bound to the solid phase are held in a magnetic field, while

unbound materials are washed away. The chemiluminescent substrate

Lumi-Phos 530 is added to the vessel and light generated by the

reaction is measured with a luminometer. The light production is

inversely proportional to the concentration of thyroxine in the sample.

The amount of analyte in the sample is determined from a stored,

multipoint calibration curve. (Package insert:  Beckman Coulter Ireland

Inc., Ireland, 2005)

Performing Laboratory Location

Rochester

Key