Dust mite control measures don’t help asthma patients

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PURLs

Dust mite control measures don’t help asthma patients

J Fam Pract. 2008 December;57(12):789-792

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References

1. Gotzsche PC, Johansen HK. House dust mite control measures for asthma. Cochrane Database Syst Rev. 2008;(2):CD001187.-

2. German JA, Harper MB. Environmental control of allergic diseases. Am Fam Physician. 2002;66:421-426.

3. National Asthma Education and Prevention Program (NAEPP). Control of environmental factors and comorbid conditions that affect asthma. In: Expert panel report 3: guidelines for the diagnosis and management of asthma. Bethesda, Md: National Heart, Lung, and Blood Institute; 2007.

4. National Environmental Education & Training Foundation (NEETF). Environmental management of pediatric asthma. Guidelines for health care providers. Washington, DC: National Environmental Education & Training Foundation (NEETF); 2005.

5. Gøtzsche PC, Hammarquist C, Burr M. House dust mite control measures in the management of asthma: meta-analysis. BMJ. 1998;317:1105-1110.

6. Hammarquist C, Burr ML, Gotzsche PC. House dust mite control measures for asthma. Cochrane Database Syst Rev. 2000;(2):CD001187.-

7. Gøtzsche PC, Johansen HK, Burr ML, Hammarquist C. House dust mite control measures for asthma. Cochrane Database Syst Rev. 2001;(3):CD001187.-

8. Gøtzsche PC, Johansen HK, Schmidt LM, Burr ML. House dust mite control measures for asthma. Cochrane Database Syst Rev. 2004;(4):CD001187.-

9. Schmidt LM, Gøtzsche PC. Of mites and men: reference bias in narrative review articles: a systematic review. J Fam Pract. 2005;54:334-338.

10. Platts-Mills TA, Tovey ER, Mitchell EB, Moszoro H, Nock P, Wilkins SR. Reduction of bronchial hyperreactivity during prolonged allergen avoidance. Lancet 1982;2:675-678.

11. Grootendorst DC, Dahlen SE. Benefits of high altitude allergen avoidance in atopic adolescents with moderate to severe asthma, over and above treatment with high dose inhaled steroids. Clin Exp Allergy. 2001;31:400-408.

12. Morgan WJ, Crain EF, Gruchalla RS, et al. Results of a home-based environmental intervention among urban children with asthma. N Engl J Med. 2004;351:1068-1080.

13. American Academy of Family Physicians. Dust mites in the home [patient handout]. Available at: http://familydoctor.org/online/famdocen/home/common/asthma/triggers/683.html. Accessed October 23, 2008.

14. American Academy of Pediatrics. Non-pharmacologic approaches to asthma management [patient handout]. Available at: http://www.aap.org/sections/allergy/nonrxchild.pdf. Accessed October 23, 2008.

15. Bailey W. Patient information: Trigger avoidance in asthma. UpToDate [online database]. Version 16.2. Waltham, Mass: UpToDate; 2008.

WHAT’S NEW?: Nothing is new, yet this will be “news” to many

This Cochrane review includes 5 additional trials that have been conducted since the last Cochrane review of this topic in 2004. However, the 2004 review reported the same conclusion—that interventions to reduce house dust mite exposure in asthma patients are ineffective—as did 3 other Cochrane reviews on the same topic beginning in 1998.^5-8

So why are the guidelines out of step? Schmidt and Gøtzsche (one of the authors of the Cochrane review) conducted a systematic review of narrative review articles in 2005 to answer this question. They found 70 review articles, 90% of which recommended physical methods to reduce exposure to house dust mites. They discovered that although these review articles included references to support their recommendations of dust mite control measures, the reviews showed significant bias in favor of positive studies and highlighted the results of low-quality studies, including non-randomized studies that had been excluded from the Cochrane reviews.⁹

CAVEATS: Duration of studies not long enough?

We know that extreme measures to reduce exposure to dust mite allergen, such as relocating to a high altitude or prolonged hospitalization, can reduce asthma symptoms,^10,11 but these are clearly not practical solutions for most patients with dust mite-sensitive asthma. When it comes to this Cochrane review, some might argue that many of the interventions included were not of sufficient duration and did not sufficiently reduce the level of house mite allergen to improve asthma symptoms.

However, the subgroups of trials with long treatment duration (1-2 years) and successful mite reduction (determined by different methods, including mite counts and measured antigen levels in dust samples) also failed to show a significant difference between intervention and control groups.¹

Tweak the approach? Most dust mite-sensitive asthma patients are sensitive to other allergens, so perhaps multifaceted interventions that target multiple allergens would be more effective.¹² But until these potential interventions are supported by stronger evidence, we should not recommend them to our patients.

CHALLENGES TO IMPLEMENTATION: Swimming against the tide is never easy

Although the evidence to date indicates that interventions to reduce home dust mite exposure are ineffective, there are hundreds of products—including mattress and pillow covers ($10-$100), ionizers ($100-$200), and air filtration systems ($500-$800)—that are being marketed to patients with asthma. In addition, patient education handouts from sources such as the American Academy of Family Physicians, the American Academy of Pediatrics, and UpToDate recommend implementing dust mite control measures to reduce dust mite allergen exposure.^13-15

FAST TRACK

Despite a lack of evidence, patient handouts from the American Academy of Family Physicians and the American Academy of Pediatrics still recommend dust mite control measures

We need to start educating our asthma patients properly so they can spend their time, energy, and money on interventions, such as medications, that work—and not on interventions that make no difference.

Acknowledgements

The PURLs Surveillance System is supported in part by Grant Number UL1RR024999 from the National Center for Research Resources, a Clinical Translational Science Award to the University of Chicago. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.

This study was selected and evaluated using FPIN’s Priority Updates from the Research Literature (PURL) Surveillance System methodology. The criteria and findings leading to the selection of this study as a PURL can be accessed at www.jfponline.com/purls.