title: Time-resolved immunofluorometric assay for the ovarian carcinoma-associated antigenic determinant CA 125 in serum.
abstract: A time-resolved immunofluorometric assay (IFMA) is described for quantifying the ovarian carcinoma-associated antigenic determinant CA 125 in human serum. Monoclonal antibody to CA 125 is immobilized onto a microtiter well, and the same antibody labeled with a europium chelate is used as a tracer. After the immunoreaction the bound portion of the labeled antibody is quantified by dissociating the Eu3+ in a fluorescence-enhancement solution and measuring its fluorescence with a time-resolved fluorometer. The detection limit of the IFMA is 1.5 arb. units/mL, being about the same as that of a commercially available immunoradiometric assay (IRMA) for CA 125 (1.4 arb. units/mL). The analytical range of the IFMA extends to 2000 arb. units/mL, whereas the range of the IRMA is 500 arb. units/mL. For 29 serum samples from ovarian-cancer patients measured simultaneously in the IFMA and IRMA, orthogonal regression analysis gave the equation CA 125 (IFMA) = 0.9937 CA 125 (IRMA) - 1.211 arb. units/mL (Syx = 6.8681, r = 0.9932). Apparently, the IFMA for CA 125 is a convenient alternative to the IRMA for CA 125 because of short counting times, the use of nonradioactive, stable reagents, and the much-extended measuring range. Additionally, the microtiter format should lend itself to more fully automated procedures in laboratories doing many such analyses.
mesh_terms: D000951:Antigens, Neoplasm / Q000032:analysis*; D015295:Antigens, Tumor-Associated, Carbohydrate; D003536:Cystadenocarcinoma / Q000276:immunology*; D000939:Epitopes / Q000032:analysis*; D005260:Female; D005470:Fluorometry; D006801:Humans; D010051:Ovarian Neoplasms / Q000276:immunology*; D011863:Radioimmunoassay
chemical_list: D000951:Antigens, Neoplasm; D015295:Antigens, Tumor-Associated, Carbohydrate; D000939:Epitopes