An immunoperoxidase assay for serum ragweed-specific IgE.

A solid-phase enzyme immunoassay for allergen-specific IgE antibodies in serum is descirbed. In this technique these antibodies are allowed to bind to the allergen previously adsorbed to the wells of polystyrene microtiter plates. After a washing step the tubes are incubated with rabbit antihuman IgE labelled with horseradish peroxidase. Following a second washing step, the enzyme bound to the tubes is assayed spectrophotometrically using O-phenylene diamine as the substrate. The standard curves obtained with this method and with the RAST technique are illustrated. For the assay of serum antiragweed IgE antibodies, concordance between the results obtained with the RAST test and this immunoperoxidase assay was observed in 85 or 95 (90%) patients with symptoms of ragweed hayfever. The coefficients of variation ranged from 4.4% (2SD +/- .010) TO 14% (2SD +/- .008). The advantages of using peroxidase as the enzymatic marker for the assay of allergen-specific IgE are discussed.