title: Immunoassay of insulin-like growth factor binding protein-1.
abstract: Accurate measurement of insulin-like growth factor (IGF) binding protein-1 (IGFBP-1) is important for precise definition of its physiological roles and potential diagnostic values. Because altered phosphorylation results in altered IGFBP-1 immunoreactivity, current assays may significantly underestimate or fail to detect physiological changes in the IGFBP-1 concentrations. We developed three ELISAs (ELISA 1-3) using a common capture but three different detection antibodies. IGFBP-1 in serum, synovial fluid (SF), cerebrospinal fluid (CSF), and amniotic fluid (AF) were measured before and after treatment with alkaline phosphatase (ALP). Among the methods, only ELISA-1 was unaffected by IGFBP-1 phosphorylation and generated identical results before and after ALP treatment. The serum and SF values by ELISA-2 and -3 were lower by approximately 4- to 10-fold, but increased after ALP treatment to within 66-98% of those by ELISA-1. The medians in AF, and to a lesser extent in CSF, by all methods were similar and did not change significantly after dephosphorylation. ELISA-1 showed excellent correlation with ELISA-2, ELISA-3, and a commercial IGFBP-1 IRMA only after ALP-treated samples were analyzed by the comparative methods. ELISA-1 is highly specific for IGFBP-1 and demonstrated acceptable analytical performance characteristics.
authors.affiliation: Diagnostic Systems Laboratories (Canada) Inc., Toronto, ON.
authors.forename: M J
authors.initials: MJ
authors.lastname: Khosravi
authors.forename: A
authors.initials: A
authors.lastname: Diamandi
authors.forename: J
authors.initials: J
authors.lastname: Mistry
mesh_terms: D000469:Alkaline Phosphatase; D000653:Amniotic Fluid / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal; D002555:Cerebrospinal Fluid / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000032:analysis* / Q000097:blood / Q000276:immunology; D051379:Mice; D010766:Phosphorylation; D015203:Reproducibility of Results; D013582:Synovial Fluid / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D018970:Insulin-Like Growth Factor Binding Protein 1; D000469:Alkaline Phosphatase