THE RELATIONSHIP BETWEEN RAST AND SKIN-TEST RESULTS IN PATIENTS WITH ASTHMA OR RHINITIS - A QUANTITATIVE STUDY WITH PURIFIED MAJOR ALLERGENS

Background: Study of the relationship between skin test results and Ig E antibody levels is seriously hampered by the use of conventional all ergen extracts because the precise amount of relevant allergen for eac h patient is unknown. Objective: This study was designed to investigat e skin reactivity with purified major allergens and to assess the rela tion with serum levels of IgE antibodies and to determine which additi onal factors contribute to the skirt test result. Methods: We used fiv e purified major allergens (Der p 1, Der p 2, Fel d 1, Lol p 1, and Lo l p 5) in skin tests, RASTs, and histamine release tests in 43 multise nsitized patients with asthma or rhinitis. Results: The differences in biologic activity of the five major allergens at a given level of spe cific IgE art within one order of magnitude. A significant residual va riation remains in the correlation between skin test the results and l evels of IgE antibodies, which cannot be explained by imprecision of b oth tests (Pearson log skirt test vs log specific IgE: r = -0.46-0.92) . With similar levels of specific IgE, the amount of allergen that is required for a positive skin test result may differ by as which as a f actor of 100 between patients. The amount of total IgE in serum contri butes significantly to the skirl test result. High values of total IgE are accompanied by a lower skin reactivity for allergen. Within indiv iduals, allergens that cause skin test results that deviate from the p rediction based on IgE antibody level often show a similar deviation i n the histamine release test. This indicates that die type of lgE resp onse (i.e., affinity or epitope recognition pattern) contributes signi ficantly to the skin test result. Skin reactivity for histamine does n or significantly influence the skin reactions expressed as allergen th reshold However; increased skin reactions with higher allergen dosages depend on histamine reactivity. Conclusion: The major allergens teste d show similar biologic activities. In addition to IgE antibody level, total serum IgE and type of IgE antibody response contribute signific antly to rite skirt test threshold for allergens. Even in a system wit h purified allergens, IgE antibody levels and skin test results are no t interchangeable as an indicator of the degree of allergic sensitizat ion.