Serum thyrotropin as measured with a one-step monoclonal-antibody radioimmunometric assay compared with two commercial radioimmunoassay kits.

We compared results obtained with a commercial immunoradiometric assay kit for human thyrotropin in which monoclonal antibodies are used (Tandem -R TSH (ONE STEP) ImmunoRadioMetricAssay; Hybritech Inc.) with those obtained with two commercial radioimmunoassay methods: GAMMA-DAB [125I]HS-hTSH RIA (Clinical Assays) and Thyro-SHure TSH Diagnostic Kit (Nuclear Medical Laboratories). The correlation of all results obtained in the Hybritech assay with those of the two commercial RIAs exceeded 95%. Mean values for 100 euthyroid samples measured in the Hybritech assay were lower than for the other two methods. The separation between hyperthyroid and euthyroid patients was much clearer with the Hybritech assay than with the RIA methods. The Hybritech assay was far more sensitive than the Clinical Assays or the Nuclear Medical Laboratories assay.