House dust mite avoidance measures improve peak flow and symptoms in patients with allergy but without asthma: A possible delay in the manifestation of clinical asthma?,☆☆,,★★

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Abstract

Background: Asthma caused by allergy to house dust mite is a growing problem. Patients with allergy who do not have asthma (yet) might develop asthma depending on exposure to precipitating factors. Objective: We sought to determine whether house dust mite avoidance measures have an effect on the development of asthma. Methods: Patients with allergy (n = 29) who had no diagnosis of asthma (FEV1 of 99.1% ± 10.6% of predicted, peak flow variability of 5.21% ± 3.41%, reversibility of FEV1 after 400 μg salbutamol of 3.92% ± 3.75% according to the reference values) were randomly allocated (subjects blinded) to a treatment (n = 16) and a placebo group (n = 13). House dust mite avoidance treatment consisted of applying Acarosan (Allergopharma, J. Ganzer KG, Hamburg, Germany) (the placebo group used water) to the floors (living room, bedroom), and the use of covers for mattresses and bedding that were impermeable to house dust mite (the placebo group used cotton covers for mattresses only). We tested whether the intervention had an effect on peak flow parameters and asthma symptom scores during 6 weeks of treatment. Results: Significant improvements were seen in the treatment group in symptom scores (Borg score) for disturbed sleep, breathlessness, wheeze, and overall symptom score. Slight but statistically significant improvements in peak flow (morning, evening, and variability) were seen in the treatment group also. No significant changes were seen in the placebo group. Conclusions: Although this study is not long enough to study the development of asthma, the results indicates that house dust mite avoidance measures had an effect on peak flow parameters and asthma symptoms in patients with allergy but without asthma. These findings might implicate that a shift in developing clinically manifest asthma could be achieved with house dust mite avoidance measures. To give a better answer to whether preventing the development of asthma is possible, larger studies with a longer follow-up period are necessary. (J Allergy Clin Immunol 1997;100:313-9.)

Section snippets

Patients

Patient characteristics are given in Table I. Patients were recruited after their general practitioners referred them to the hospital for intradermal skin testing. All patients had an allergy test because they had some very mild signs of asthma (mostly early morning dyspnea or wheeze), but none had a diagnosis of asthma. After this test, patients remained under the medical care of the general practitioner and not of a specialist. Patients were excluded if they had a confirmed diagnosis of

Patient characteristics

Twenty-nine patients were included in the study. After randomization and stratification, a slightly unbalanced distribution was achieved, with 16 patients in the treatment group and 13 patients in the placebo group. Patient characteristics are shown in Table I. Only age differed significantly between the groups, in that the treatment group was older than the placebo group (31 vs 24 years). In all analyses, the difference in age had no influence on any of the effects studied (n values always

Discussion

Sufficient evidence has accumulated to confirm a close relation between sensitivity to mite allergens and asthma. 7, 29, 30 A causal relationship between mite allergen sensitization and the development of asthma seems plausible. 3, 8, 31 Consequently, in some patients allergy might be an indication of a genetic disposition for asthma; in other words, allergy might be considered in these patients as a subclinical (early) expression of asthma. Therefore, in these patients, preventing further

Acknowledgements

We thank Mr. R. Akkermans for his statistical support.

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    From the aDepartment of General Practice and Social Medicine and bDepartment of Pulmonary Diseases, Medical Centre Dekkerswald, University of Nijmegen, the cDepartment of Allergy, University of Groningen, and the dDepartment of Epidemiology and Public Health, University of Wageningen.

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    Supported by the Dutch Asthma Foundation, by CIBA, and by 3M Pharma Industries.

    Reprint requests: Dr. S.G.M. Cloosterman, Department of General Practice and Social Medicine, 229, University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.

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