Specificity of two-site immunoassays

Lynette M. Boscato*, Gregory M. Egan, Margaret C. Stuart

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


When cross-reaction in two-site immunoassays was investigated both theoretically and experimentally it was found that such systems do not always result in enhanced specificity. Computer simulation studies indicated that substances which display negligible cross-reaction in a radioimmunoassay could produce an assay response identical to that of the analyte in a two-site immunoassay using excess antibody. Cross-reactivity in two differing two-site immunoassays was compared to that obtained in radioimmunoassays using the same monoclonal antibodies for human chorionic gonadotrophin. In addition to the effects of excess antibody, cross-reactivity was observed in one of the two-site immunoassays which could not have been predicted from the specificity of the antibodies or cross-reactivity in the radioimmunoassays. The unexpected cross-reaction of the β subunit of human chorionic gonadotrophin in the assay resulted from an apparent alteration in the specificity of one of the antibodies following binding of the β subunit to the second antibody. These studies emphasise the complexity of binding reactions in two-site immunoassays.

Original languageEnglish
Pages (from-to)221-229
Number of pages9
JournalJournal of Immunological Methods
Issue number2
Publication statusPublished - 24 Feb 1989


  • Assay specificity
  • Chorionic gonadotropin
  • Monoclonal antibody
  • Two-site immunoassay


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