Variability in the measurement of specific immunoglobulin E antibody by the RAST procedure

This is a report of a study from the Committee on In Vitro Tests of the American Academy of Allergy, which evaluated variance of the RAST procedure when different allergic sera were tested by 12 Committee member laboratories using the Phadebas RAST kit (Pharmacia Diagnostics, Piscataway, N.J.) and when serial dilutions of a ragweed allergic sera were sent to nine different commercial laboratories in the U.S.A. The Phadebas RAST was found to differentiate high-, medium-, and low-titer allergic sera. The test was not useful in measuring smaller changes (less than 61%) in specific IgE antibody that might result from treatment with immunotherapy. Alternative methods of reporting the data, percent total activity and percent negative control, were not superior to the Phadebas RAST unit. Four of the commercial laboratories surveyed did not differentiate by their own measure of significance medium- from low-titer ragweed allergic sera.