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Competitive Immunoassay

Detect antigens with a single antibody

Competitive Immunoassay


A competitive immunoassay enables detection of an antigen (target) with use of a single capture antibody attached to the surface of a microsphere and a competitive, labeled antigen reversibly bound to the antibody. An analyte of interest in the sample competes with the labeled antigen causing a decrease in detected signal. A reverse version of the assay is also possible in which the analyte in the sample competes away the labeled antibody in solution rather than on the surface of the microsphere. A version of competitive assays on xMAP® Technology was used extensively in the development of the Gardasil® vaccine.


Applications include:

  • Small molecules
  • Peptides
  • Drug-interaction studies

GARDASIL® is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, NJ, U.S.A.