Background: Inner-city asthma is well known for its high risk of mortality. To better understand urban asthma, we examined clinical characteristics and aeroallergen sensitivities of 592 of 680 consecutive urban Chicago residents with asthma.
Methods: A total of 227 male and 453 female subjects who met the criteria for the study were registered. A comprehensive clinical evaluation was followed by allergy skin testing (prick and intradermal testing) with 10 groupings (5 indoor and 5 outdoor) of common aeroallergens. Serum total IgE and selective antigen-specific IgE levels, including cockroach-specific IgE, were routinely measured. A total of 592 (196 male and 396 female) subjects with an average age of 35 years were skin tested. The average duration of asthma was 12.6 years, and 31% of the population was receiving corticosteroids.
Results: Aeroallergen sensitivity was noted in 85%, and 94 subjects (15%) were nonallergic. House dust sensitivity (76%) was most prevalent, distantly followed by sensitivity to cockroach (48%), ragweed (45%), other weeds (42%), cat (40%), and dust mite (24%). The average number of aeroallergen sensitivities detected was 4 of 10 groupings of both indoor and outdoor allergens. Twenty percent of subjects were allergic to only indoor allergens, whereas 4% were allergic to outdoor allergens only. Serum IgE was 245 +/- 17.3 IU/ml (geometric mean+SEM), and 74% of 444 serum samples showed IgE antibody levels greater than or equal to 100 IU/ml. A cockroach-sensitive subgroup (283 subjects) had longer duration of asthma (p < 0.0001) and fewer additional aeroallergen sensitivities (p < 0.0001) than the ragweed-sensitive subgroup (264 subjects).
Conclusion: The results indicate that a great majority (85%) of inner-city Chicago residents with asthma have atopic asthma, as demonstrated by highly elevated IgE levels and multiple aeroallergen sensitivities. Sensitivity to indoor allergens is more prevalent than sensitivity to outdoor allergens. The subjects with cockroach-sensitive asthma appear to be a distinctive subgroup characterized by chronicity and elevated serum IgE antibody levels with fewer aeroallergen skin test sensitivities.