Cell-free detection of allergen-IgE cross-linking with immobilized phase CD23: Inhibition by blocking antibody responses after immunotherapy

The positive predictive value was 91%, and the negative predictive value was 100% (see Table E2 in this article's Online Repository at www.jacionline.org). [...]the inhibitory activity of postimmunotherapy sera against allergen-IgE-dependent binding to CD23 appears similar when measured by using either the ELIFAB or IgE-FAB assays. [...]the ELIFAB assay represents a simple reproducible means for measuring the ability of allergen to cross-link IgE. IgE-FAB (gold standard) ELIFAB Positive Negative Total Positive 42 4 46 Negative 0 38 38 Totals 42 42 84 Table E2 Sensitivity and specificity of the ELIFAB assay versus IgE-FAB assay Eighty-four serum samples were obtained from 21 subjects who received either subcutaneous grass pollen immunotherapy (7 subjects receiving a maintenance dose of 10,000 SQ-U and another 7 receiving 100,000 SQ-U) or placebo (7 subjects) in a clinical trial.8 A test result was considered positive if sera inhibited allergen-IgE binding with an indicator serum by greater than 15%.