The most widely used assay for in vitro potency of allergenic extract is the RAST inhibition method. This test is a variation of the direct RAST. Serum from an allergic individual (containing IgE) is first mixed with the soluble unknown allergen. Next, a standard amount of the solid-phase (immobilized) allergen is added. The more "potent" the fluid phase allergen, the less IgE is free to bind to the solid-phase allergen ( 32). The technique and its statistical analysis have been standardized. RAST inhibition usually is the key technique to assess total allergenic activity of an extract and is used by manufacturers to calibrate new batches by comparison with the in-house reference preparation. Recently, some workers have raised concern regarding the continued use of RAST inhibition as a standard technique ( 33). The arguments concern the fact that the choice of antigen for the solid-phase reaction is variable and may influence results. In addition, the finite supply of allergenic reference sera limits reproducibility: without identical reference sera and immobilized allergen, comparisons are impossible. Further development of monoclonally derived IgE and recombinant allergens may help with this problem.
Was this article helpful?