A new tumour marker assay for ovarian cancer on the OPUS immunoassay system

The human tumour associated cancer antigen CA 125 is a glycoprotein with high molecular weight. The determination of this antigen has been proven to be useful in the monitoring of patients with ovarian cancer. OPUS OV, the tumour marker assay for the ovarian cancer antigen CA 125 is an ELISA that was developed for the family of fully automated random-access analyzers, OPUS, OPUS Plus and OPUS I Magnum. The assay uses a double monoclonal sandwich format (antibodies B27.1 and B43.13, Biomira/Canada). The first antibody is immobilized on the solid phase of the OPUS modules. Sample is automatically added and incubated for 5 minutes. The addition of a solution of the second antibody conjugated to the enzyme alkaline phosphatase leads to the formation of a sandwich complex within 5 minutes. The last step, the addition of the fluorogenic substrate 4-methylumbelliferyl phosphate, serves both as washing procedure and for the development of the fluorescence signal (kinetic measurement). OPUS OV has an assay range from 0-1000 kU/L with a detection limit of 5 kU/L. Within run cv's are 6-8%. A good correlation was found to commercially available kits for the determination of CA 125. We conclude that this new OPUS OV assay is a valid alternative for use in the routine determination of the cancer associated antigen CA 125 and allows more reliable determinations in terms of random access, speed, and ease of operation.