Influence of house dust mite impermeable covers on health-related quality of life of adult patients with asthma: results of a randomized clinical trial

The aim of this study was to evaluate the effect of house dust mite impermeable covers on asthma-specific health-related quality of life in adult asthmatic patients that were trained in guided self-management. In a 2-year randomized placebo-controlled clinical trial, information on the quality of life was collected. The improvement of Mini Asthma Quality of Life Questionnaire (AQLQ) score in the allergens-avoidance group (0.26) was comparable to the improvement in the placebo group (0.30) and not significant. HDM-impermeable covers for pillows, duvets, and mattresses did not result in improved health-related quality of life.

House dust mite allergen avoidance and self-management in allergic patients with asthma: randomised controlled trial

BACKGROUND

The efficacy of bed covers that are impermeable to house dust mites has been disputed.

AIM

The aim of the present study was to investigate whether the combination of 'house dust mite impermeable' covers and a self-management plan, based on peak flow values and symptoms, leads to reduced use of inhaled corticosteroids (ICS) than self-management alone.

DESIGN OF STUDY

Prospective, randomised, double blind, placebo-controlled trial.

SETTING

Primary care in a south-eastern region of the Netherlands.

METHOD

Asthma patients aged between 16 and 60 years with a house dust mite allergy requiring ICS were randomised to intervention and placebo groups. They were trained to use a self-management plan based on peak flow and symptoms. After a 3-month training period, the intervention commenced using house dust mite impermeable and placebo bed covers. The follow-up period was 2 years. Primary outcome was the use of ICS; secondary outcomes were peak expiratory flow parameters, asthma control, and symptoms.

RESULTS

One hundred and twenty-six patients started the intervention with house dust mite impermeable or placebo bed covers. After 1 and 2 years, significant differences in allergen exposure were found between the intervention and control groups (P<0.001). No significant difference between the intervention and control groups was found in the dose of ICS (P = 0.08), morning peak flow (P = 0.52), peak flow variability (P = 0.36), dyspnoea (P = 0.46), wheezing (P = 0.77), or coughing (P = 0.41). There was no difference in asthma control between the intervention and control groups.

CONCLUSION

House dust mite impermeable bed covers combined with self-management do not lead to reduced use of ICS compared with self-management alone.

Relationship between house dust mite (HDM) allergen exposure level and inhaled corticosteroid dosage in HDM-sensitive asthma patients on a self management program

AIM

To assess whether exposure to house dust mite (HDM) allergens hampers a tapering off of inhaled corticosteroid (ICS) dosage in HDM-sensitive asthma patients.

METHODS

Asthma patients sensitised to HDM allergens and using ICS were selected from general practices for this observational study. Dust samples from bed mattresses were taken to assess exposure ('no', 'low', 'intermediate' or 'high') to HDM allergens with a semi-quantitative test (Acarex). Patients were trained to use a self management plan to adjust the dose of ICS according to symptoms and peak flow. The observation period was three months.

RESULTS

Outcomes from 123 patients were analysed. Within the 'no' and 'low' HDM exposure groups the proportion of patients who increased the dosage of their ICS medication was significantly lower than the proportion who tapered off or remained on the same dose of ICS. The group with high exposure to HDM allergens had the highest proportion of patients who increased their dose of ICS (p = 0.055).

CONCLUSIONS

High exposure to HDM allergens seems to coincide with the use of higher dose ICS treatment in asthma patients sensitised to HDM allergens.

Factors associated with asthma control

The aim of this study was to evaluate which factors are associated with asthma control experienced by asthma patients. In a cross-sectional study patients aged 16-60 years with mild to moderate asthma were selected. The influence of the following factors on asthma control was studied in a multivariate model: age, gender, socioeconomic status, smoking, perceived hyperresponsiveness (PHR, responding with asthma symptoms to one or more triggers), allergy (Phadiatop), long-acting bronchodilating agents, and inhaled corticosteroids. Asthma control was measured by means of the Asthma Control Questionnaire (ACQ) as developed by Juniper. Forced expiratory volume in 1 second (FEV1) was measured by means of a portable spirometer. In this study with 311 patients, mean ACQ score was 1.39 (range 0-4.43). A stepwise backward linear regression analysis showed that low socioeconomic status (beta 0.425; p=0.001), current smoking (beta 0.555; p<0.001), high dose of inhaled corticosteroids (beta 0.364; p=0.04) and perceived hyperresponsiveness for increasing number of different triggers (PHR for 1 trigger beta 0.833; p=0.03; 2 triggers beta 0.810; p=0.03; 3 triggers beta 0.995; p=0.01; 4 triggers beta 1.131; p=0.002; 5 triggers beta 1.182; p=0.002) are independent predictors for poorer asthma control. Beside treatment with medication, stopping smoking and avoidance of triggers are factors, which may have a high impact on asthma control.

Clinical effectiveness of a mite allergen-impermeable bed-covering system in asthmatic mite-sensitive patients

BACKGROUND

Exposure to allergens plays a role in the development of bronchial hyperresponsiveness and in the chronic inflammatory response seen in asthmatic patients. House dust mites (HDMs) are an important source of allergen. Reduction of these allergens might lead to better lung function and reduction of asthma symptoms.

OBJECTIVE

The effect of HDM-impermeable covers on HDM allergen levels, peak flow values, and asthma symptoms were measured. Therefore a randomized clinical trial was carried out.

METHODS

Fifty-two allergic asthmatic patients were randomly allocated to use the HDM-impermeable or placebo covers. During the study period, daily peak flow and asthma symptom scores were recorded. Dust samples were taken from the mattresses.

RESULTS

We observed a significant reduction in HDM allergen levels on the mattresses after encasing them with HDM-impermeable covers (reduction of 87% of Der p 1 in micrograms per gram of dust; P <.001). Baseline symptoms were so low that no improvement could be established. Morning peak expiratory flow is significantly higher in the intervention group compared with that seen in the placebo group during the study period (beta=20.2; P <.01).

CONCLUSIONS

HDM-impermeable covers significantly decreased the level of HDM allergens. Furthermore, morning peak flow was significantly increased during the intervention period. This study indicates that HDM allergen-avoidance measures might have beneficial effects on allergen reduction and asthma outcome.