A high sensitivity immunochemiluminometric assay for human thyrotrophin.

A two-site immunochemiluminometric assay (ICMA) has been developed for the measurement of human thyrotrophin (TSH). The procedure involves reaction of serum samples with monoclonal antibodies to TSH which have been labelled with a chemiluminescent acridinium ester followed by reaction with solid-phase polyclonal antibodies to TSH. The total reaction time is 2 h and bound labelled antibody is quantified luminometrically. The assay has an absolute sensitivity of 0.004 mU/l and a linear dose-response range up to 60 mU/l. Circulating TSH concentrations in 84 normal subjects were in the range 0.4 to 4.0 mU/l and in 16 hyperthyroid patients were less than 0.03 mU/l. This assay should thus prove useful as a first line test of thyroid function.