Solid phase immunoradiometric assay for CA125 antigen levels in blood using monoclonal antibodies
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We have developed a simple one step ‘sandwich’ immunoradiometric assay for CA125 using monoclonal antibodies directed against two different epitopes of the antigen. The detection antibody was radiolabeled with I-125 and the selected capture antibody was chemically coupled to magnetizable cellulose to form immobilized solid support. In the developed inclusive assay procedure, 200 μL of standard or sample was incubated with 100 μL of radiolabeled and capture antibody suspension for 18 h at room temperature with shaking. At the end of the incubation, the sandwich complex attached to solid phase is separated and counted for associated radioactivity. The analytical sensitivity for the developed assay procedure was observed to be 3.0 U/mL with an assay range up to 500 U/mL of CA125. The developed assay displayed acceptable precision; expressed in terms of percentage Coefficient of Variation (CV) estimated by repeated analyses of the quality control samples. Intra-assay CV was observed to be less than 5% whereas inter-assay CV was also less than 6%. The analytical recovery of the developed assay observed to be in the range of 88–107%. The clinical samples analyzed by the developed procedure showed a good correlation with that of a commercial kit (r = 0.99; y = 1.0052x − 38.942).
KeywordsImmunoradiometric CA125 antigen Tumor marker Ovarian carcinoma
Authors thank Dr. A. K. Kohli, Chief Executive, BRIT for his support. The authors are also thankful to Shri. Harish Chander, General Manager, (Labelled Compounds) for extending continuous encouragement for publication of this work. Our sincere thanks to Dr. Vijay Kadwad for providing the magnetic particles and helpful discussions in the early stages of the work.
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