Fluoroimmunoassay: an alternative to radioimmunoassay?

Fluoroimmunoassays appear to be an alternative to conventional radioimmunoassays and immunoradiometric assays because of the high specific activity of their label, thus promising high sensitivity and excellent precision. According to IFCC recommendations for the assessment of new laboratory methods, we evaluated precision, accuracy, linearity, lower detection limit and normal reference ranges of commercially available immunofluorometric assays of alpha-fetoprotein, choriongonadotropin and thyrotropin. In addition, thyrotropin content in sera of 147 patients was measured by immunofluorometric assay. Analysis of immunofluorometric assays gained performance data comparable to those of currently used immunoradiometric assays. Regression studies performed against currently employed methods showed accuracy of all three immunofluorometric assays. Results of immunofluorometric assay for thyrotropin demonstrated that sera of hyperthyroid subjects were distinguished from those of euthyroid subjects from basal thyrotropin alone. We conclude that immunofluorometric assays are an alternative to immunoradiometric assays which anybody concerned about the future of in vitro nuclear medicine should be aware of.