Immunoassay of total insulin-like growth factor binding protein-1

An immunoassay method for the detection of total insulin-like growth factor binding protein- 1 in a fluid comprising the steps of:

• a) contacting a sample of fluid suspected of containing insulin-like growth factor binding protein-1 with a first capture antibody that binds to total insulin-like growth factor binding protein-1 to form a complex, wherein said first capture antibody is unaffected by the degree of phosphorylation of insulin-like growth factor binding protein-1, and wherein said first capture antibody is bound to a solid carrier, said solid carrier being insoluble in said fluid;
• b) contacting the complex with a second detecting antibody, wherein said second detecting antibody is unaffected by the degree of phosphorylation of insulin-like growth factor binding protein-1 and wherein said second detecting antibody is labeled;
• c) separating said solid carrier from said fluid sample and unreacted second detecting antibody;
• d) measuring either the amount of labeled second detecting antibody associated with the solid carrier or the amount of unreacted labeled second detecting antibody;
• and
• e) relating the amount of labeled antibody measured with the amount of labeled antibody measured for a control sample prepared in accordance with steps (a)-(d), said control sample being known to be free of insulin-like growth factor binding protein, to determine the presence of total insulin-like growth factor binding protein in said fluid sample, or relating the amount of labeled antibody measured with the amount of labeled antibody measured for samples containing known amounts of insulin-like growth factor binding protein prepared in accordance with steps (a)-(d) to determine the concentration of total insulin-like growth factor binding protein in said fluid sample.