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The role that house dust mites play in the primary causation of asthma is controversial. Approximately thirty-six 10-yr-old children in each of 10 centres in the Asia-Pacific region participated. Researchers collected dust from mattresses and living room floors using standardized procedures. Der p1 and Der f1 were analysed using a double monoclonal antibody enzyme-linked immunosorbent assay. Geometric mean allergen levels were calculated for each centre. An ecological analysis was conducted to show the regression of the geometric mean allergen level, using the highest household level, against asthma symptom and severity prevalence data from the International Study of Asthma and Allergies in Childhood, Phase I. Among children aged 13-14 yr, the change in asthma symptom prevalence was associated with per unit change in Der p1 microg/g (1.08, 95% CI 0.10-2.06) and Der 1 microg/g (Der p1 + Der f1) (0.64, 95% CI 0.02-1.26). The change in having four or more attacks of asthma in the last 12 months was associated with per unit change in Der p 1 microg/g (0.29, 95% CI -0.02 to 0.60) and Der 1 microg/g (0.20, 95% CI 0.01-0.38). There was no effect for total Der p1 or Der f1 (total or microg/g). Among children aged 6-7 yr, neither allergen was related to symptoms or severity prevalence. While our findings suggest that Dermatophagoides pteronyssinus may have a role in the primary causation of asthma, the complexity of this association reinforces the need for prospective studies.

OBJECTIVE This study aimed to determine the relationship between individual allergens with current wheezing and bronchial hyperresponsiveness (BHR) in schoolchildren from three chinese cities: Beijing, Guangzhou and Hong Kong. METHODS Community-based random samples of 10-yr-old schoolchildren from the 3 cities were recruited for study using the International Study of Asthma and Allergies in Childhood (ISAAC) Phase II protocol. The subjects were studied by parental questionnaires (n = 10,902), skin-prick tests (n = 3478), and methacholine challenge tests (n = 608). RESULTS The highest prevalence rates of wheezing in the past 12 months (Beijing, 3.8%; Guangzhou, 3.4%; Hong Kong, 5.8%) and atopy (Beijing, 23.9%; Guangzhou, 30.8%; Hong Kong, 41.2%, defined as having

The role of allergen sensitization in the development of asthma in the Chinese is not clear. This study aims to determine the relationship of sensitization to individual allergens, and the development of asthma and bronchial hyperresponsiveness (BHR) in schoolchildren from three Chinese cities: Hong Kong, Beijing and Guangzhou. Community-based random samples of 10-yr-old schoolchildren from three Chinese cities were recruited for study using the International Study of Asthma and Allergies in Childhood (ISAAC) Phase II protocol. Subjects were studied by parental questionnaires (n=10,902), skin-prick tests (n=3,479), and methacholine challenge tests (n=608). The prevalence rates of wheeze in the past 12 months (Hong Kong, 5.8%; Beijing, 3.8%; Guangzhou, 3.4%) and atopy (Hong Kong, 41.2%; Beijing, 23.9%; Guangzhou, 30.8%) were highest in schoolchildren from Hong Kong. Multivariate logistic regression analyses revealed that sensitization to Dermatophagoides pteronyssinus (odds ratio (OR)=4.48; 95% confidence interval (CI): 3.02-6.66), cat (2.59; 1.67-4.03), Dermatophagoides farinae (2.41; 1.65-3.51) and mixed grass pollen (2.85; 1.24-6.50) were significantly associated with current wheeze. Atopy, defined as having > or = 1 positive skin-prick tests, was not an independent risk factor for current wheeze in children from any of the three cities. Furthermore, atopy (OR=2.53; 95% CI: 1.07-5.97), sensitization to cat (3.01; 1.39-6.52) and D. farinae (3.67; 1.93-6.97) were significantly associated with BHR. The authors confirmed that sensitization to house dust mite and cat was significantly associated with current wheeze and bronchial hyperresponsiveness in Chinese schoolchildren. However, the difference in the prevalence rate of atopic sensitization cannot explain the higher prevalence of childhood asthma in Hong Kong, when compared with those children from Beijing and Guangzhou.

Background: The prevalence of asthma and allergic disease has been increasing in Hong Kong and environmental factors are thought to play a major role., Aim: To define the distribution of common inhaled allergens and air pollutants inside residential homes in Hong Kong., Methods: Forty randomly selected residential homes were visited and surveyed. Dust samples were collected from mattress, bedroom floor, lounge room floor and kitchen floor for assays of Der p 1, Fel d 1, and Bla g 2. Nitrogen dioxide (NO2) levels were measured by stationary samplers left in the bedroom, lounge room and kitchen over a 1-week period., Result: All 40 homes were apartments in high-rise buildings and the mean age of the homes was 7.6 +/- 4.8 years. Visible dampness and mould patches were present in 27.5% of homes and the main fuel for cooking was gas (97.5%). Der p 1, Fel d 1 and Bla g 2 were detectable in at least 1 niche in over 85% of homes. In particular, all dust samples from mattress and bedroom floor contained Der p 1, and over 50% had levels > or = 2 microg/g. The (geometric) mean Der p 1 level in mattress dust was 8.8 (0.3-157.8) microg/g. Fel d 1 and Bla g 2 were present in low levels throughout the homes with respective (geometric) means of 0.3 (0-3.7) microg/g and 0.1 (0-1.1) Unit/g in mattress dust. NO2 was readily detected in all niches but the highest level was in the kitchen with mean exposure of 48.7 ppb which was 1.5 times higher than that in the bedroom and lounge room., Conclusion: Major allergens of mite, cat and cockroach, and NO2 are present in varying quantities in residential homes in Hong Kong. Exposure to these environmental factors could be important in the development of asthma and allergic diseases in susceptible individuals.

Background: Allergen sensitization is associated with asthma and allergic disease in children, but such a relationship has not been confirmed in Chinese populations., Objectives: The objective of this study was to evaluate the effects of allergen sensitization and family history of atopy on asthma and allergic disease in Chinese schoolchildren from three southeast Asian populations., Methods: Written questionnaires on respiratory and allergic symptoms were completed by parents of children of secondary-school age (age range 12 to 18 years) in Hong Kong (n = 1062), Kota Kinabalu in eastern Malaysia (n = 409), and San Bu in southern China (n = 737). A subsample of school-children underwent skin prick testing to common inhalant allergens (Hong Kong 471 children, Kota Kinabalu 321, San Bu 647)., Results: The prevalence of asthma and allergic disease in schoolchildren was highest in Hong Kong, intermediate in Kota Kinabalu, and lowest in San Bu. However, the overall rate of atopic sensitization was similar in the three populations (49% to 63%). House dust mite and cockroach were the two most common allergens causing sensitization and these gave rise to more than 95% of the positive skin test results in all three populations. By regression analysis, mite allergy was associated with rhinitis and asthma in all three populations, and a family history of asthma, rhinitis, or eczema was strongly associated with respective symptoms in the subjects. After adjusting for age, sex, atopic status, and family history of allergic disease, the place of residence remained a significant independent factor for asthma (odds ratio [OR] = 1.0 for Hong Kong, 0.57 for Kota Kinabalu, 0.15 for San Bu, p < 0.001), rhinitis (OR = 1.0 for Hong Kong, 0.59 for Kota Kinabalu, 0.15 for San Bu, p < 0.001), or eczema (OR = 1.0 for Hong Kong, 0.35 for Kota Kinabalu, 1.01 for San Bu, p < 0.001)., Conclusion: Sensitization to indoor allergens was a significant risk factor for asthma and allergic disease, and familial clustering of disease was common in the region. However, the marked difference in disease prevalence in the three southeast Asian populations of Chinese schoolchildren cannot be explained by atopic sensitization and family history alone, and the place of residence was an independent risk factor for asthma and allergies, which suggests an important environmental role in disease pathogenesis.

We have attempted to use a potent and selective histamine H1-receptor antagonist terfenadine to allow a larger dose of allergen to be administered to previous single early responders to investigate if an increased dose of allergen could induce a late asthmatic response. Pre-treatment with 180 mg of terfenadine enabled a geometric mean increase in allergen dose of 4.12-fold to be inhaled by eight atopic subjects with mild asthma, who initially were classified as single early responders, with maximal fall in FEV1 3-8 hr after allergen challenge (Lmax) of less than 15% from baseline value. The magnitude of early asthmatic response was similar to that obtained on the control day when allergen challenge was performed in the absence of terfenadine. Two subjects were converted to dual responders with Lmax of 23.1 and 24.3%, which occurred with a 32- and 65-fold increase in allergen dose respectively, and a 6- and 4.9-fold decrease in non-specific airways responsiveness measured as the cumulative provocative concentration of methacholine that caused a 20% fall in FEV1 from baseline. The remaining six subjects failed to achieve an Lmax of greater than 10% even with a 1.29-2.66-fold increase in allergen dose. For the group as a whole an increase in allergen dose was associated with an increase in overall bronchoconstrictor response 3-8 hr after challenge. These results indicate that it is possible to induce a late asthmatic response in a subject who previously demonstrated only an early response by increasing the dose of allergen inhaled.

We have used a short-acting beta 2-adrenoceptor agonist, rimiterol hydrobromide, to allow a larger dose of allergen to be administered to previous single "early allergen responders" to investigate if an increased dose of allergen could induce a late asthmatic response (LAR) and whether this would influence the subsequent level of allergen-acquired nonspecific bronchial hyperresponsiveness. Pretreatment with inhaled rimiterol hydrobromide 400 microgram enabled an increase in allergen dose inhaled by a geometric mean of 8.9-fold (range, 2 to 29.1) in eight atopic subjects with mild asthma who initially were classified as single early responders with a maximal fall in FEV 3 to 8 h after allergen challenge (Lmax) of less than 15% from baseline value. The magnitude of the early asthmatic response was similar to that obtained on the control day when allergen challenge was performed in the absence of rimiterol hydrobromide. Five subjects were converted to dual allergen responders with Lmax of greater than 15% from premedication baseline value. For the whole group, there was a significant increase in the magnitude of LAR whether calculated as Lmax (p less than 0.05) or as area under the FEV1 time response curve between 3 and 8 h postchallenge (p less than 0.01). The provocation concentrations of methacholine causing a 20% fall in FEV1 (PC20) at 8 h postchallenge were significantly reduced on both days when compared with the corresponding prechallenge values (p less than 0.05 on control day, p less than 0.01 on rimiterol day). However, despite the increase in the magnitude of LAR on the rimiterol day, the reduction in postchallenge PC20 did not differ significantly from that occurring on the control day.(ABSTRACT TRUNCATED AT 250 WORDS)