Latex allergosorbent test (LAST): a new immunoassay for specific IgE with latex particles

We describe a two-step latex (Lx) agglutination assay for the titration of specific anti-Dermatophagoides pteronyssinus IgE. The samples are first incubated with allergen-coated Lx of 2.3 microns diameter. Bound IgE is digested by pepsin and then titrated by its agglutinating activity on 0.8 micron Lx particles coated with antihuman Fc epsilon rabbit F(ab')2. This latex allergosorbent test detects 100 pg of specific IgE per milliliter and does not depend on the concentration of total IgE. Owing to a tenfold increase in the allergosorbent surface, no competition with the binding of specific anti-D. pteronyssinus IgG is observed. Pepsin digestion eliminates potential interferences caused by autoantibodies against IgE. A good correlation (r = 0.92) is found with Phadebas RAST on a series of 91 samples. The latex allergosorbent test does not make use of radioisotopes and can be performed in less than 6 hours.