title: Sensitive human thyrotropin immunoradiometric assay set up by the identification and minimization of nonspecific bindings.
abstract: An immunoradiometric assay (IRMA) of human thyrotropin (hTSH), based on magnetic solid phase separation, was studied especially in terms of its nonspecific bindings (B0) which were identified as a product of the interaction between an altered form of radioiodinated anti-hTSH monoclonal antibody (125I-mAB) and the uncoupled magnetizable cellulose particle (matrix). Preincubation with the same matrix, solid phase saturation with milk proteins, tracer storage at 4 degrees C and serum addition during incubation were found to be particularly effective in preventing their formation. These findings were used to reproducibly decrease nonspecific bindings to values < 0.1% (or < 70 cpm), thus increasing the signal-to-noise ratio (B60/B0) up to values of 300-500. This way hTSH radioassays were obtained with functional sensitivities of about 0.05 mIU/L and analytical sensitivities of the order of 0.02 mIU/L. Such sensitivities, and, more importantly, a general improvement in assay performance, were obtained in a highly reproducible manner and all over the useful tracer life.
authors.affiliation: Department of Application of Nuclear Techniques in Biological Sciences, National Nuclear Energy Commission (IPEN-CNEN), São Paulo, Brazil.
authors.forename: C N
authors.initials: CN
authors.lastname: Peroni
authors.forename: M T
authors.initials: MT
authors.lastname: Ribela
authors.forename: P
authors.initials: P
authors.lastname: Bartolini
mesh_terms: D000327:Adsorption; D004355:Drug Stability; D052203:Ferrosoferric Oxide; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods*; D007457:Iodine Radioisotopes; D007501:Iron; D010087:Oxides; D011485:Protein Binding / Q000276:immunology; D012680:Sensitivity and Specificity; D013972:Thyrotropin / Q000032:analysis* / Q000276:immunology* / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D010087:Oxides; D013972:Thyrotropin; D007501:Iron; D052203:Ferrosoferric Oxide