House dust mite control measures for asthma.

backgroundThe major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites.

objectivesThe objective of this review was to assess the effects of reducing exposure to house dust mite antigens in the homes of mite-sensitive asthmatics. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, checked reference lists of articles and hand-searched Respiration (1980 to 1996) and Clinical and Experimental Allergy (1980 to 1996). The Cochrane Library is searched every three months. SELECTION CRITERIA: Randomised trials of mite control measures vs placebo or no treatment in asthmatic people known to be sensitive to house dust mites. DATA COLLECTION AND ANALYSIS: Two reviewers applied the trial inclusion criteria, assessed their quality and extracted the data independently. Study authors were contacted to clarify information. MAIN

resultsTwenty-nine trials (939 patients in the analyses) were included, with two trials awaiting assessment. There was little difference in improvement of asthma between patients in experimental groups compared to control groups (relative risk 1.04, 95% confidence interval (95%CI) 0.83 to 1.31). Asthma symptom scores were also similar for the experimental and control groups (standardised mean difference (SMD) -0.07, 95% CI -0.35 to 0.22), however there was significant heterogeneity between studies p=0.015. This appears to have been due, in part, to the parallel group studies of physical treatments. These three studies (107 patients) showed a significant reduction in symptoms; SMD -0.44 (95% CI -0.83, -0.06) with no heterogeneity between the trials. No significant difference was noted for medication usage (SMD -0.14, 95%CI -0.43 to 0.15). Peak flow in the morning showed no significant difference between the experimental and the control groups (SMD 0.04, 95%CI -0.13 to 0.21). REVIEWER'S

conclusionsCurrent chemical methods aimed at reducing exposure to house dust mite allergens seem to be ineffective and cannot be recommended as prophylaxis for mite sensitive asthmatics. Physical reduction methods may reduce asthma symptoms, but results of larger and more rigorous studies are required before any recommendations can be made concerning this approach.