Chemiluminescent labeled-antibody assay for thyroxin in serum, with magnetic separation of the solid-phase.

A chemiluminescent labeled-antibody immunoassay has been developed for measurement of total thyroxin (T4) in serum. Monoclonal antibodies to T4 labeled with a chemiluminescent acridinium ester are used. Serum samples are incubated with the labeled antibodies and a thyroxin-rabbit immunoglobulin conjugate, then reacted with magnetizable particles containing sheep anti-rabbit immunoglobulin. The total reaction time is 40 min. The chemiluminescence intensity of the solid-phase immune complexes is inversely proportional to the concentration of T4 in the sample. The sensitivity of the assay is 1 nmol/L, and the working range of 20-190 nmol/L is characterized by CVs less than or equal to 10%.