PRACTICE RECOMMENDATIONS
Allergen-impermeable bed covers, as a single intervention, are ineffective for the management of asthma symptoms in adults. They are also ineffective for patients with allergic rhinitis.1
Q&A
Impermeable bed covers ineffective for asthma
- BACKGROUND: Patients with asthma who are allergic to dust mites experience more severe symptoms when exposed to high levels of dust mite allergen. Mite-allergen-impermeable bed covers reduce the level of exposure to allergens, but it is unknown whether they reduce asthma symptoms.
- POPULATION STUDIED: The investigators sent letters to 21,045 patients aged 18 to 50 years with physician diagnosed asthma who were regularly taking inhaled steroids. Patients already using allergen-impermeable bed covers or using less than 100 μg of albuterol daily were excluded. Most (1150) of 1431 patients were able to complete a daily diary card during the 4-week run-in period and were entered into the study.
- STUDY DESIGN AND VALIDITY: Patients were randomized and matched for pet ownership, smoking status, and mite-specific immunoglobulin E (IgE) levels. Randomization was designed to ensure balance between the randomized groups at each practice in the study. Patients received either mattress, pillow, and quilt covers impermeable to mite allergen or ordinary control covers. The covers were fitted by a research nurse.
- OUTCOMES MEASURED: Examiners evaluated patients’ morning peak expiratory flow rate during phase 1; secondary outcomes measured were evening peak expiratory flow rate, use of beta-agonists, subjective scores for daytime and nighttime symptoms, number of days of work missed, and subjective quality-of-life scores during the last 4 weeks of phase 1. During phase 2, examiners evaluated the proportion of patients who discontinued inhaled corticosteroid therapy, with a secondary outcome of proportionate reduction in the dose of inhaled corticosteroid.
- RESULTS: Differences between the intervention and control groups in the primary and secondary outcome measures were not significant at the end of phase 1 or phase 2. Both the intervention and the control group patients demonstrated small but statistically significant improvement in peak expiratory flow rate (from 410.7 to 419.1 L/min in the intervention group, and from 417.8 to 427.4 L/min in the control group), and a substantial reduction in inhaled corticosteroid use during the study period (47% in the intervention group and 48% in the control group).