Radioimmunoassay and Automated Enzyme Immunoassay for the Determination of Thyroxine

The EMIT homogeneous enzyme immunoassay for the determination of thyroxine (T4) was adapted to an automatic analyser (Type Kem-O-Mat) and compared with a conventional radioimmunoassay. Sera from 92 patients whose thyrometabolic status was being examined, and control sera with 3 different T4 concentrations were analysed by both methods. Day-to-day analyses of the control sera gave variation coefficients between 6 and 10% for both methods. The mean value for T4 in the patients sera was 111 nmol/l (8.6 microgram/dl) determined by the enzyme immunoassay and 109 nmol/l (8.5 microgram/dl) determined by the radioimmunoassay; the correlation coefficient was r = 0.9.