| abstract |
The invention relates to an assay system for the improved detection of analytes, and the ability to distinguish them from cross-reacting substances. Samples giving a positive reaction in a direct assay test are treated with a neutralizing antibody that inhibits reactivity of the true analyte, but not the interfering substance. In adsorption type confirmatory assays, the neutralizing antibody is provided in an amount sufficient to adsorb the analyte but not all of the interfering substance. When retested in an immunoassay, the neutralized sample gives a negative result if it originally contained the true analyte. Samples giving a positive reaction in both the direct and confirmatory tests are marked as containing an interfering substance. The confirmatory assay easily distinguishes the true analyte and reduces the rate of false positives, even when the interfering substance is unknown and present at high concentration. |