Cat allergen level:: Its determinants and relationship to specific IgE to cat across European centers

Background: Cat allergen level in settled house dust and its determinants in Europe are unknown. Objective: The aim of this study is to quantify the level of cat allergens in mattress dust, to study its determinants, and to analyze the relationship with cat specific IgE on community level across European centers. Methods: Trained field workers collected dust from approximately 3000 mattresses during home visits in 22 European Community Respiratory Health Survey II centers. Sieved dust extracts were assayed for cat allergen using a mAb ELISA assay. Results: The overall geometric mean cat allergen was 0.94 mu g/g, ranging from 0.12 mu g/g in Huelva, Spain, to 3.76 mu g/g in Antwerp, Belgium. Current cat owners' homes showed substantially higher levels than past cat owners' and never cat owners' homes (geometric mean and 95% CI, 61.4 mu g/g [48.4-77.9] vs 1.37 mu g/g [0.97-1.9] vs 0.29 mu g/g [0.27-0.31]x). Community prevalence of cat ownership was moderately correlated with cat allergen levels in noncat owners (r(s) = 0.50), but not for past or current cat owners. The multilevel model identified community prevalence of cat keeping as the only statistically significant determinant of mattress cat allergen levels for noncat owners. However, averaged cat allergen levels per center were not related to community prevalence of detectable specific IgE to cat. Conclusion: Not having a cat in the home is associated with substantially lower Fel d 1 concentration, but does not protect against high Fel d 1 exposure in communities where cat ownership is common. Clinical implications: People (including patients with cat allergy) who do not own cats may be exposed to high levels of cat allergen in their home, particularly if they live in communities with high levels of cat ownership.