A new and universal free/bound separation technique for the "CENTRIA" automated radioimmunoassay system.

A new separation procedure based on the double-antibody technique has been adapted to the CENTRIA System. This procedure is universally applicable and lends itself to easy adaptation to commercial RIA kits in which liquid reagents are used. This second antibody is covalently linked to agarose (Sepharose) and the lyophilized powder is subsequently tableted for easy use on the instrument. The technique was applied to radioimmunoassay for thyrotropin (thyroid stimulating hormone), alpha-fetoprotein, and ferritin. Performance characteristics were as follows: sensitivity 1.5 milliunits/L, 4.5 micrograms/L, and 4.5 micrograms/L, respectively; intrarun precision 1.7, 9, and 3.4%, and interrun precision 7.6, 13, and 14.5%. All three assays were clinically validated.