House dust mite control measures in the management of asthma: meta-analysis

BMJ 1998;317:1105-1110 ( 24 October )

Papers

House dust mite control measures in the management of asthma: meta-analysis

Editorial by Strachan

Peter C Gøtzsche, director, ^a Cecilia Hammarquist, director, ^b Michael Burr, consultant. ^c

^a Nordic Cochrane Centre, Rigshospitalet, Department 7112, DK-2200 Copenhagen N, Denmark, ^b Executive Office, Unit of Public Health, Municipality of Gotland, S-62181 Visby, Sweden, ^c Centre for Applied Public Health Medicine, University of Wales College of Medicine, Cardiff CF1 3NW

Correspondence to: Dr Gøtzsche p.c.gotzsche{at}cochrane.dk

Objective To determine whether patients with asthma who are sensitive to mites benefit from measures designed to reducetheir exposure to house dust mite antigen in thehome.
Design Meta-analysis of randomised trials that investigated the effects on asthma patients of chemical or physicalmeasures to control mites, or both, in comparison with an untreatedcontrol group. All trials in any language were eligible forinclusion.
Subjects Patients with bronchial asthma as diagnosed by a doctor and sensitisation to mites as determined by skin pricktesting, bronchial provocation testing, or serum assays for specificIgEantibodies.
Main outcome measures Number of patients whose allergic symptoms improved, improvement in asthma symptoms, improvementin peak expiratory flow rate. Outcomes measured on different scaleswere combined using the standardised effect size method (the differencein effect was divided by the standard deviation of themeasurements).
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 comparedwith 38/117 in the control groups (odds ratio 1.20, 95% confidenceinterval 0.66 to 2.18). The standardised mean difference for improvementin asthma symptoms was $-$ 0.06 (95% confidence interval $-$ 0.54 to0.41). For peak flow rate measured in the morning the standardisedmean difference was $-$ 0.03 ( $-$ 0.25 to 0.19). As measured in theoriginal units this difference between the treatment and the controlgroup corresponds to $-$ 3 l/min (95% confidence interval $-$ 25 l/minto 19 l/min). The results were similar in the subgroups of trialsthat reported successful reduction in exposure to mites or hadlong follow uptimes.
Conclusion Current chemical and physical methods aimed at reducing exposure to allergens from house dust mites seemto be ineffective and cannot be recommended as prophylactic treatmentfor asthma patients sensitive tomites.

Key messages

Current chemical and physical methods aimed at reducing exposure to allergens from house dust mites seem to be ineffective; these methods cannot be recommended as prophylactic treatment for asthma patients who are sensitive to mites
It is unlikely that a worthwhile effect has been overlooked in this meta-analysis since the confidence interval for the peak expiratory flow rate was quite narrow
Future studies should be much larger and more rigorous than those in this meta-analysis and should evaluate other methods of mite control than those used to date

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Rapid Responses:

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Poor validity?: Ingegerd Larsson
bmj.com, 27 Oct 1998 [Full text]
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bmj.com, 26 Oct 1998 [Full text]
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bmj.com, 12 Nov 1998 [Full text]
The peak flow of a population is not a valid measure of asthma: David S Morrison
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