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Immunoassay for the in vitro quantitative determination of total thyroxine in human serum and plasma.

The Elecsys® test principle is based on competition principle. Total duration of assay: 18 minutes (37°C). • 1st incubation (9 minutes): Sample (15 µL) and a specific anti-T4 antibody labeled with a ruthenium complex (75 uL). • 2nd incubation (9 minutes): After addition of biotinylated T4 (75 uL) and streptavidin-coated microparticles (35 uL), the still-free binding sites of the labeled antibody become occupied, with formation of an antibody-hapten complex. The entire complex is bound to the solid phase via interaction of biotin and streptavidin. •The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier (0.4 second read frame). •Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent bar code.