EVALUATION OF HOUSEHOLD DUST-MITE EXPOSURE AND LEVELS OF SPECIFIC IGEAND IGG ANTIBODIES IN ASTHMATIC-PATIENTS ENROLLED IN A TRIAL OF IMMUNOTHERAPY

Background: Monitoring the response to immunotherapy entails understan ding exposure to relevant allergens. For the major indoor allergens, t his requires sampling of dust from the patient's house. The objectives of this study were to measure indoor allergen levels during a control led trial of dust mite immunotherapy for asthma and to relate these re sults to serum antibody levels. Methods: Eighty-eight asthmatic patien ts with mite allergy from seven geographic areas in the United States were enrolled in and completed a course of immunotherapy with Dermatop hagoides extract or placebo control. Sensitization was evaluated by qu antitative measurements of IgG and IgE antibodies. Dust samples were a ssayed for group I mite (Der p I and Der f 1), cat (Fel d 1), and cock roach (Bin g 1) allergens by monoclonal antibody-based ELISA. Results: Over the 4 years of the study, each of the houses had at least one sa mple that contained more than 2 mu g of group I mite allergen pet gram of dust. Mean mite allergen levels, however varied over a wide range, from 0.2 mu g/gm or less to more than 50 mu g/gm. IgE antibodies to m ite were present in sera from 78% of the patients whereas IgE antibodi es to cat and cockroach allergens were found in sera from 34% and 11% of patients, respectively. Sixty-four percent of the patients had expo sure and sensitization to mite, whereas the comparable figure for each of the other allergens was 5%. Conclusions: Examination of the result s suggested that allergen exposure, relative to a trial of immunothera py, could be expressed as (1) the maximum level found in the house, (2 ) the percentage of sites having greater than 2 mu g/gm, or (3) the me an value at the site with the maximum level. This report provides a ba ckground for evaluating the clinical results of immunotherapy in these patients and a model for the way in which sensitization and exposure should be monitored in studies of this kind.