Radioimmunoassay and immunoradiometric assay for TSH-measurement

The comparison of a TSH-RIA providing satisfactory results in clinical routine work (lower detection limit 0.5 μU/ml) with a newly developed TSH-IRMA using four different antibodies and B/F separation by magnetic fields did not show clear-cut improved diagnostic facilities in the IRMA. Lower detection limit was slightly lower (0.4 μUy/ml) with clearly higher values in the upper ranges in the IRMA. The precision of the IRMA is good over the whole range of concentrations, whereas this is not possible within one incubation scheme by RIA. The technical procedure of the IRMA is easier and to be performed in 3 hours, however, in the diagnostically important low concentration ranges the count rates are very low with demand on longer counting time and special care avoiding even smallest contaminations or accidental radiation in the surrounding of the counter. (orig.)