Study population

The study design was based on case/control comparisons of 72 subjects nested within the 14 year follow-up of The Western Australian Pregnancy (Raine Study) Cohort, an unselected longitudinal birth cohort, representative of the West Australian population [11]. The study population was stratified into three groups; HDM-sensitized atopics with current asthma (n = 22), HDM-sensitized atopics without current asthma (n = 26) and HDM-nonsensitized controls (without current asthma, n = 24). Current asthma was assessed by questionnaire, and was defined as a doctor diagnosis of asthma ever, plus the use of any asthma medication in the last 12 months, plus wheeze in the last 12 months. Total IgE was measured by ImmunoCAP (Phadia) from serum samples for all participants, as was Phaditop IgE; the Phadiatop test (Phadia) uses an ImmunoCAP with a balanced mix of representative inhalant allergens. Specific IgE to the following allergens was measured (ImmunoCAP, Phadia): HDM (Dermatophagoides pteronyssinus), rye grass pollen (Lolium perenne), cat, couch grass (Cynodon dactylon), mold mix (Penicillium notatum, Cladosporium herbarum, Aspergillus fumigatus, Candida albicans, Alternaria alternata, and Helminthosporium halodes), peanut, and food mix (egg white, milk, fish, wheat, peanut, and soybean). Sensitization to an allergen was defined as specific IgE ≥0.35kU/L.