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[Results of a multicenter evaluation of enzyme immunoassays for thyrotropin (TSH)]
This paper summarises the results of the evaluation of an enzyme immunoassay for thyrotropin by a group of 17 laboratories. This sandwich enzyme immunoassay is based on the specific binding of the beta-subunit of thyrotropin by monoclonal antibodies coated on polystyrene tubes. Thyrotropin, bound to the tube wall, is determined with horse radish peroxidase coupled to the Fab fragment of a polyclonal sheep antibody against the alpha-subunit of thyrotropin. The lower limit of detection of 0.5 mU/1 was adequate, and the precision of the enzyme immunoassay was comparable with that found in radioimmunoassays for thyrotropin. The intraassay CV was in the range of 2 to 10% for a serum containing 1.5 to 5 mU/1 thyrotropin. The interassay CV was in the range of 5 to 10% for a serum containing about 6 mU/1. The recovery of thyrotropin standards in human thyrotropin-free serum was between 93% and 101%. Cross-reactions with human choriongonadotropin and gonadotropins were excluded. There were no interferences in haemolytic and lipaemic samples or by high bilirubin concentrations. Comparison of thyrotropin levels measured with different radioimmunoassays and with the enzyme immunoassay gave correlation coefficients in the range of 0.925 and 0.995. Advantages of the enzyme immunoassay are the absence of radioactive substances and the short incubation period of 3 hours. Incubation overnight results in a higher sensitivity of 0.18 mU/1. This assay can therefore be regarded as one of the new highly sensitive thyrotropin assays (Bernutz, C. et al. (1985) Clin. Chem. 31, 289-292).
This paper summarises the results of the evaluation of an enzyme immunoassay for thyrotropin by a group of 17 laboratories. This sandwich enzyme immunoassay is based on the specific binding of the beta-subunit of thyrotropin by monoclonal antibodies coated on polystyrene tubes. Thyrotropin, bound to the tube wall, is determined with horse radish peroxidase coupled to the Fab fragment of a polyclonal sheep antibody against the alpha-subunit of thyrotropin. The lower limit of detection of 0.5 mU/1 was adequate, and the precision of the enzyme immunoassay was comparable with that found in radioimmunoassays for thyrotropin. The intraassay CV was in the range of 2 to 10% for a serum containing 1.5 to 5 mU/1 thyrotropin. The interassay CV was in the range of 5 to 10% for a serum containing about 6 mU/1. The recovery of thyrotropin standards in human thyrotropin-free serum was between 93% and 101%. Cross-reactions with human choriongonadotropin and gonadotropins were excluded. There were no interferences in haemolytic and lipaemic samples or by high bilirubin concentrations. Comparison of thyrotropin levels measured with different radioimmunoassays and with the enzyme immunoassay gave correlation coefficients in the range of 0.925 and 0.995. Advantages of the enzyme immunoassay are the absence of radioactive substances and the short incubation period of 3 hours. Incubation overnight results in a higher sensitivity of 0.18 mU/1. This assay can therefore be regarded as one of the new highly sensitive thyrotropin assays (Bernutz, C. et al. (1985) Clin. Chem. 31, 289-292).