Method of assay

In an assay for an analyte, a sample of biological fluid is first incubated with first insoluble particles carrying a specific binder for the analyte. The supernatant liquid, containing potentially interferring species, is discarded. The analyte/specific binder complex is treated, e.g. with enzyme, to re-solubilize the analyte or an antigenically distinctive fragment thereof. To the resulting assay fluid, second insoluble particles are added and their agglutination is measured, either by turbidimetry or by particle counting. The method is particularly suitable for identifying IgE antibodies directed against specific allergens in serum or plasma.