Contribution of dust mite and cat specific IgE to total IgE: Relevance to asthma prevalence

BackgroundThe prevalence of asthma is strikingly different in some Westernized countries: ∼20% in New Zealand and ∼8% in northern Sweden.ObjectiveWe investigated differences in total IgE and in the prevalence of wheezing related to the observation that high exposure to dust mite allergens induces high titers of IgE antibodies.MethodsTwo age-matched, population-based cohorts—1155 children in New Zealand (224 sera) and 3431 children (797 sera) in the Norrbotten area of Sweden—were studied. Sera were assayed for total IgE and specific IgE antibodies to relevant allergens.ResultsThe mean total IgE among wheezing children was higher in New Zealand than Sweden (218 IU/mL vs 65.2 IU/mL; P < .001). In addition, the prevalence of high titer specific IgE antibody (≥50 IU/mL) was greater among the wheezing children in New Zealand compared with Sweden (35.7% vs 13.0%; P < .001). Specific IgE antibody to mite in New Zealand was significantly related to high total IgE (≥200 IU/mL; r = 0.47; P < .001), whereas the IgE antibody response to cat allergens did not make a significant contribution to high total IgE in either country.ConclusionThe quantity of IgE antibody produced to dust mite provides a possible explanation for the higher total IgE levels found in children in New Zealand and may help to explain the differences in prevalence and severity of asthma between these 2 countries.Clinical implicationsSpecific IgE antibody responses to dust mite and cat allergens may contribute differently to total serum IgE and to the prevalence of allergic disease.