Seasonal asthma in northern California: allergic causes and efficacy of immunotherapy

Inland areas of northern California have an intense grass pollination in the spring of each year. This is accompanied by a stirking rise in the incidence of asthma. We documented this relationship and designed a trial to test the efficacy of immunotherapy for grass-pollen asthma. Aeroallergen counts were performed on the roof of the allergy clinic of David Grant Medical Center from January 1981 to December 1984 by a gravity collector. These counts were compared to counts done on a Rotorod at a nearby hospital from July 1982 to September 1984. Climatologic factors were also tabulated. Visits for asthma and rhinitis to our emergency room and asthma admissions to our hospital were counted for the 4-year period. A randomized, double-blinded, placebo-controlled trial of immunotherapy with grass-pollen extract was performed from November 1984 to June 1985. Two groups of clinically and immunologically well-matched subjects were started on an accelerated preseasonal trial of immunotherapy. One group received a standardized grass extract, and the other group did not. Both groups received other extracts of aeroallergens to which they were skin test positive that occur locally in the spring and summer. This was done because of our dissatisfaction with a histamine placebo used in a previous pilot study. Symptom medication scores (SMS) and immunologic parameters were followed. For the 4-year period, grass-pollen count (GPC) correlated strongly with asthma emergency room visits (r = 0.90; p less than 0.001) and for rhinitis (r = 0.92; p less than 0.001). Asthma admissions also correlated strongly with GPC (r = 0.72; p less than 0.001). Other aeroallergens either did not correlate significantly or occurred in such small numbers that they could not be seriously considered. Rotorod counts supported these conclusions with the exceptions of some Basidiomycetes. Climatologic factors demonstrated no relationship to the incidence of asthma. Asthma SMS were lower in the grass-treated group, p less than 0.05. Rhinitis SMS were also lower but did not reach significance, p = 0.11. RGGI sIgE did not rise significantly in the grass-treated group but did in the placebo-treated group. RGGI sIgE rose in both groups, although to significantly higher levels in the grass-treated group, p less than 0.001. The asthma SMS were inversely related to increasing RGGI cumulative dose, p less than 0.10. Linear regression analysis of the dose-response scattergram suggests that a cumulative dose of approximately 90 micrograms of RGGI may be desirable.(ABSTRACT TRUNCATED AT 400 WORDS)