House dust mite control measures in the management of asthma: meta-analysis.
OBJECTIVE
To determine whether patients with asthma who are sensitive to mites benefit from measures designed to reduce their exposure to house dust mite antigen in the home.


METHODS
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 untreated control group. All trials in any language were eligible for inclusion.


METHODS
Patients with bronchial asthma as diagnosed by a doctor and sensitisation to mites as determined by skin prick testing, bronchial provocation testing, or serum assays for specific IgE antibodies.


METHODS
Number of patients whose allergic symptoms improved, improvement in asthma symptoms, improvement in peak expiratory flow rate. Outcomes measured on different scales were combined using the standardised effect size method (the difference in effect was divided by the standard deviation of the measurements).


RESULTS
23 studies were included in the meta-analysis; 6 studies used chemical methods to reduce exposure to mites, 13 used physical methods, and 4 used a combination. 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 difference for improvement in asthma symptoms was -0.06 (95% confidence interval -0.54 to 0.41). For peak flow rate measured in the morning the standardised mean difference was -0.03 (-0.25 to 0.19). As measured in the original units this difference between the treatment and the control 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 that reported successful reduction in exposure to mites or had long follow up times.


CONCLUSIONS
Current chemical and physical methods aimed at reducing exposure to allergens from house dust mites seem to be ineffective and cannot be recommended as prophylactic treatment for asthma patients sensitive to mites.
Gøtzsche
P C
PC
Nordic Cochrane Centre, Rigshospitalet, Department 7112, DK-2200 Copenhagen N, Denmark. p.c.gotzsche@cochrane.dk
Hammarquist
C
C
Burr
M
M
D000485:Allergens / Q000009:adverse effects*; D000818:Animals; D001249:Asthma / Q000503:physiopathology / Q000517:prevention & control*; D004391:Dust / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D007300:Insect Control / Q000379:methods*; D008925:Mites; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D016032:Randomized Controlled Trials as Topic
D000485:Allergens; D004391:Dust