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

Background: The prevalence of asthma is strikingly different in some Westernized countries: approximately 20% in New Zealand and approximately 8% in northern Sweden.
Objective: We 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.
Methods: Two 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.
Results: The 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 (> or =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 (> or =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.
Conclusion: The 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 Implications: Specific IgE antibody responses to dust mite and cat allergens may contribute differently to total serum IgE and to the prevalence of allergic disease.