Immunoglobulin Inhibiting Reagent: evaluation of a new method for eliminating spurious elevations in CA125 caused by HAMA.

Cancer therapy utilising radiolabelled murine monoclonal antibodies frequently leads to the production of Human Anti-Mouse Antibodies (HAMA) in the recipient. HAMA interferes with "sandwich" immunoassays, such as those for tumour markers, rendering results unreliable. Published methods for eliminating HAMA from serum are not suitable for use in a laboratory which is processing a large number of assays using an automated system. We report on the use of Immunoglobulin Inhibiting Reagent (IIR) in CA125 assays from recipients of intraperitoneal radioimmunotherapy who had spuriously elevated results due to HAMA. IIR was found to be comparable to the admixture of mouse serum as a way of eliminating the effect of HAMA. IIR is ideally suited to use with an automated assay process.