Automated radioimmunoassay of total and free thyroxine in human serum.

A rapid, automated method for the measurement of total and free thyroxine in serum by radioimmunoassay is described. The method uses a commercially available antiserum covalently coupled to finely divided cellulose. A non-equilibrium reaction provides a very fast procedure: 80 samples can be analysed for total and free thyroxine within 3 hours using the Kemtek 3000 automated immunoassay system. The method also has the advantage that a small sample volume (6.25 microliter) is required and that it yields high precision. Serum total and free thyroxine concentrations in healthy euthyroid subjects, pregnant women, and hyperthyroid and hypothyroid patients are reported.