HOUSE-DUST MITE CONTROL MEASURES IN THE MANAGEMENT OF ASTHMA - METAANALYSIS

Objective To determine whether patients with asthma who are sensitive to mites benefit from measures designed to reduce their exposure to ho use dust mite antigen in the home. Design Meta-analysis of randomised trials that investigated the effects on asthma patients of chemical or physical measures to control mites, or both, in comparison with an un treated control group. All trials in any language were eligible for in clusion. Subjects Patients with bronchial asthma as diagnosed by a doc tor and sensitisation to mites as determined by skin prick testing bro nchial provocation testing or serum assays for specific IgE antibodies . Main outcome measures Number of patients whose allergic symptoms imp roved, improvement in asthma symptoms, improvement in peak expiratory now rate. Outcomes measured on different scales were combined using th e standardised effect size method (the difference in effect was divide d by the standard deviation of the measurements). Results 23 studies w ere included in the meta-analysis; 6 studies used chemical methods to reduce exposure to mites, 13 used physical methods, and 4 used a combi nation. Altogether, 41/113 patients exposed to treatment interventions improved compared with 38/117 in the control groups (odds ratio 1.20, 95% confidence interval 0.66 to 2.18). The standardised mean differen ce for improvement in asthma symptoms was - 0.06 (95% confidence inter val - 0.54 to 0.41). For peak flow rate measured in the morning the st andardised mean difference was - 0.03 (- 0.25 to 0.19). As measured in the original units this difference between the treatment and the cont rol group corresponds to - 3 l/min (95% confidence interval - 25 l/min to 19 l/min). The results were similar in the subgroups of trials tha t reported successful reduction in exposure to mites or had long follo w up times. Conclusion Current chemical and physical methods aimed at reducing exposure to allergens from house dust mites seem to be ineffe ctive and cannot be recommended as prophylactic treatment for asthma p atients sensitive to mites.