Mite allergen (Der p 1) concentration in houses and its relation to the presence and severity of asthma in a population of Sydney schoolchildren,☆☆,

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Abstract

House dust mite (HDM) allergen exposure and its relation to HDM allergy and asthma was assessed in a case-control study conducted over three seasons in 74 Sydney schoolchildren, 33 of whom were allergic to HDM and 12 of whom had current asthma. In each season, histamine inhalation tests and skin prick tests were performed, symptom questionnaires were administered, and dust samples were collected. The mean concentrations of HDM allergen (in micrograms of Der p 1 per gram of fine dust) were: bed, 38.9 (95% confidence interval [CI], 31.8 to 47.5); bedroom floor, 22.4 (95% CI, 18.3 to 27.5); and lounge room floor, 13.7 (95% CI, 10.7 to 17.6). The mean of the highest allergen concentration in each house was 51.0 (95% CI, 43.2 to 60.1). All but two subjects had at least one site in all seasons with an HDM allergen concentration greater than 10 μg/gm, the proposed threshold for asthma symptoms. Subjects with allergy to HDM, symptoms of asthma, or airway hyperresponsiveness did not have higher HDM allergen concentrations in their houses. In this study we were unable to test hypotheses concerning proposed thresholds for risk of sensitization and for risk of asthma symptoms because virtually all subjects were exposed to HDM allergen levels above the proposed thresholds. (J Allergy Clin Immunol 1995;96:441-8.)

Section snippets

Study design

A case-control study design was used with concurrent assessment of exposure (HDM allergen concentration) and outcomes (allergy to HDM and the presence and severity of asthma). All subjects were assessed in autumn (April), winter (July), and spring (October) in 1989. On each occasion, respiratory symptoms, airway responsiveness, allergy to HDM and other allergens, symptom score, and airflow variability were measured; and dust collected from each subject's bed and floor was assayed for HDM

Subjects

Of the initial 80 subjects, six were lost to follow-up from the winter assessment and were excluded from all analyses. Of the remaining 74 subjects, all underwent skin prick testing and assessment of airway responsiveness in autumn and winter, but three were not tested in spring. The following numbers of subjects had missing questionnaire, diary card, and/or allergen data: 21 in autumn (1 questionnaire, 18 diary cards, and 6 allergen measurements), 16 in winter (14 questionnaires and fourteen

DISCUSSION

In this study we found very high HDM allergen concentrations in the household dust of schoolchildren living in western Sydney. Subjects with allergy to HDM or with current asthma did not have higher concentrations of HDM allergen in their houses than other subjects.

The concentrations of HDM allergen in this region were higher than those reported anywhere else in the world. In studies conducted in 14 centers around the world, six found mean HDM allergen concentrations of less than 10 μg/gm4, 30,

Acknowledgements

We thank the New South Wales Department of Education for allowing us to study children at their schools and all the parents and children who took part. We also thank the following members of the Institute of Respiratory Medicine staff: Ms. Melanie Shearer for field and laboratory assistance, Mr. Mark Matthews for performing the allergen assays, and Ms. Cheryl Salome for reviewing the manuscript.

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    From the Department of Medicine, University of Sydney, NSW Australia.

    ☆☆

    re-submitted in the same form June 26, 1994

    Reprints are not available.

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