Automated assay for HER-2/neu in serum

Background: The extracellular domain of the HER-2/neu oncogene:product is i ncreased in sera of some patients with epithelial cancers, Our aim was to d evelop an automated serum assay for the extracellular domain of the HER-2/n eu protein. Methods: We used a monoclonal antibody labeled with fluorescein for:capture and a monoclonal Fab' fragment labeled With alkaline phosphatase for detec tion. Separation: of bound and free detection conjugate was performed with magnetizable particles coated with monoclonal antibody to fluorescein. Alka line phosphatase activity was measured kinetically at 405 or 450 nm. Results: The assay was linear from 0.1 to 250 mu g/L. No hook effect was ev ident up to 10 000 mu g/L. Within-run imprecision (CV) was 0.8-1.2%, and to tal imprecision was 1.1-1.7%. Cross-reactivity with human epidermal growth: factor receptor, which has extensive homology with HER-2/neu extracellular domain, was <0.6%. Human anti-mouse antibodies, heterophilic antibodies, a nd rheumatoid factor did not interfere, nor did the therapeutic monoclonal antibody Herceptin(R). In 51 healthy females, the mean value was 9.3 mu g/L , with a range of 6.4-14.0 mu g/L, No reagent lot-to-lot variability was de tected over four lots of reagents tested. Conclusion: The Bayer Immune 1(TM) assay for HER-2/neu was precise and resi stant to interferences, characteristics that are essential for longitudinal monitoring of cancer patients. (C) 2000 American Association for Clinical Chemistry.