QUANTITATION OF IGG AND IGM HUMAN ANTI-MOUSE ANTIBODIES (HAMA) INTERFERENCE IN CA-125 MEASUREMENTS USING AFFINITY-CHROMATOGRAPHY

Currently no available immunoassay system offers complete protection a gainst spuriously elevated or lowered results due to interference by H uman Anti-Mouse Antibodies [HAMA). Although routine use of chromatogra phy procedures is not an acceptable option because of the extra cost a nd workload involved, such a procedure would be highly desirable to en sure accurate immunoassay results. The present report describes a rela tively simple affinity chromatography procedure using a HiTrap Protein G column to isolate immunoglobulin G (IgG) MAMA, followed by a HiTrap N-hydroxy-succinimide(NHS)-activated column coupled to goat-anti huma n immunoglobulin M (IgM) to bind IgM MAMA. To examine the usefulness o f this purification procedure we determined CA 125 in forty serum samp les prior to and following chromatography. Pre-and post-injection samp les were obtained from 20 patients injected with 1 mg of In-111-labell ed murine OC 125 F(ab')(2) fragments in an immunoscintigraphy study. I t is shown that this analytical procedure provides a technique to dete rmine the extent and the nature of the existing HAMA interference in s amples of patients after in vivo use of monoclonal antibodies for diag nostic or therapeutic purposes. The procedure can also contribute to t he clarification of clinically discordant CA 125 results. Finally, the availability of such a procedure in the clinical laboratory provides an opportunity to test the robustness of newly developed immunoassay s ystems towards HAMA interference.