Do Asthmatics Benefit from House Dust Mite Allergen Avoidance Strategies?: Results of a Systematic Review of the Literature ♦ 22

Abstract

We conducted a systematic review to determine if asthmatics who are sensitive to house dust mites (HDM) benefit from HDM allergen avoidance strategies. Using MEDLINE, a review of bibliographies, and references supplied by international experts in entomology and pediatric allergy, we identified 764 titles of English language articles, published between January, 1966 and July, 1997, which possibly included information about allergen avoidance strategies for HDM. Two investigators (MC, PE) independently reviewed the full bibliographic citation of each of the 764 candidate articles and identified 112 articles for further review. The full text of each of the 112 articles was read by two independent reviewers (MC, JZ) to identify randomized controlled trials which met the following criteria: presence of original data, intervention duration longer than eight weeks, washout period of at least four weeks for crossover trials, and a history of asthma with objective evidence of HDM sensitivity in the study population. Differences between the reviewers were resolved by consensus (MC, JZ, PE). 18 articles met the above inclusion criteria and included one or a combination of the following interventions: chemical control measures (13 articles), impermeable covers (9), aggressive cleaning (8), and/or humidity reduction (2). Studies also varied in their exclusion of study patients (i.e. severity of asthma, pet ownership, and/or tobacco exposure), as well as selection of outcome measurements, such as HDM allergen levels (12), HDM counts (5), house dust weight (3), subjective symptom scores (9), medication use (6), physician's assessment (1), lung function tests (12) and histamine/methacholine challenge tests (10). The 18 accepted articles differed in their conclusions regarding the benefit of HDM allergen avoidance measures. We conclude that the heterogeneity of interventions, exclusion criteria, and outcome measures prevents combining data among studies to calculate overall summary measures of intervention effectiveness. Furthermore, the studies suggesting a clinical benefit are qualitatively different from negative studies, since they tend to have more explicit protocols to monitor patient compliance, and tend to exclude patients on chronic steroids, patients with recent hospitalizations, and patients who own pets.