Evidence Based Effectiveness of Indoor Environmental Control for the Treatment of Allergic Asthma: Focus on House Dust Mite Allergy

Systematic study on the absence of clinical benefits of allergen avoidance for the treatment of allergic asthma

A meta-analysis of baseline characteristics in trials on mite allergen avoidance in asthmatics: Room for improvement

Background: Evidence regarding the clinical effectiveness of mite allergen avoidance for the treatment of asthma is lacking. In previous meta-analyses on mite allergen control, the baseline data were not discussed in detail. This study updates and extends the existing Cochrane review by Gøtzsche and Johansen (Cochrane Database of Systematic Reviews, 2008, Art. No: CD001187), with a focus on baseline asthma outcomes and allergen exposures. Methods: We used the existing trials in the original Cochrane review and included newly published studies. The baseline data for the mite allergen load from the mattress, the standardized asthma symptom score (ASS), the forced expiratory volume in 1 s percentage of predicted (FEV1 %pred.), and the histamine provocative concentration causing a 20% drop in FEV1 (PC20) were extracted. First, the mean values of the outcomes were calculated. The influence of the mite allergen load was examined with a random-effect meta-regression using the Metafor package in R. Results: Forty-five trials were included; 39 trials reported strategies for concurrent bedroom interventions, and 6 trails reported strategies for air purification. The mite allergen load ranged from 0.44 to 24.83 μg/g dust, with a mean of 9.86 μg/g dust (95% CI 5.66 to 14.05 μg/g dust, I2 = 99.8%). All health outcomes showed considerable heterogeneity (standardized ASS mean: 0.13, 95% CI 0.08 to 0.18, I2 = 99.9%; FEV1 %pred. mean: 85.3%, 95% CI 80.5 to 90.1%, I2 = 95.8%; PC20 mean: 1.69 mg/mL, 95% CI 0.86 to 2.52 mg/mL, I2 = 95.6%). The covariate mite allergen load did not significantly influence health outcomes. Discussion: This meta-analysis shows that mite avoidance studies are characterized by the inclusion of patients with rather mild to moderate asthma and with varying and sometimes negligible levels of allergen exposure. Future studies should focus on patients with severe asthma and increased levels of allergen exposure

Effectiveness of the Air Purification Strategies for the Treatment of Allergic Asthma: A Meta-Analysis

We updated the meta-analysis published by McDonald et al. [Chest 2002;122;1535-1542] by reviewing the effectiveness of air purification for the treatment of home-related allergic asthma (dust mite, dog, cat, and cockroach). We analysed the trials included by McDonald et al. as well as studies published since 2000. Data on asthma symptoms scores (ASS), medication use, forced expiratory volume in 1 s as a percentage of the predicted value (FEV1 %pred), histamine provocative concentration causing a 20% reduction in FEV1 (PC20), Asthma Quality of Life Questionnaire (AQLQ) scores, and fractional exhaled nitric oxide (FeNO) levels were extracted. The effectiveness was examined using metafor (registered in Prospero CRD42019127227). Ten trials including a total of 482 patients (baseline characteristics: mean FEV1 %pred 83.2%, I2 = 96.7%; mean PC20 4.93 mg/mL, I2 = 44.0%; mean AQLQ 4.67 [max. 7], I2 = 93.7%; mean FeNO 36.5 ppb, I2 = 0%) were included. We assessed the mean differences in the AQLQ scores as +0.36 (95% CI 0.10 to 0.62, p = 0.01, n = 302, I2 = 0%) and the FeNO levels as -6.67 ppb (95% CI -10.56 to -2.77, p = 0.0008, n = 304, I2 = 0%). The standardised mean differences in all other health outcomes were not significant (ASS -0.68, p = 0.20; medication use: -0.01, p = 0.94; FEV1 %pred -0.11, p = 0.34; PC20 +0.24, p = 0.53). We found statistically significant mean differences in the AQLQ scores and FeNO levels in patients with predominantly mild to moderate asthma at baseline. A large trial reported great improvement in the subgroup of patients receiving Global Initiative for Asthma step 4 therapy. We recommend that future studies on air purification focus on patients with severe and poorly controlled allergic asthma

Describing fluctuating indoor aerosol dust measurements with application to house dust mite allergens

Measuring house dust mite aeroallergen concentrations is essential in understanding mite allergen exposure. Physically, the aerolized house dust mite faeces are part of indoor particulate matter. We studied the statistical ways of summarizing measurements of fluctuating mite aeroallergen exposure inside homes through indoor particulate matter. To study emissions from beddings, we measured the time-related airborne dust concentration after shaking a duvet. Analysis was performed both by a method based on the estimated mean and by a non-linear model. Twenty-eight studies reported a sum of concentrations; only one also reported the peak. In our four experiments on shaking a duvet (245 to 275 measurements each), the peak value was two to four times higher than the mean. The mean-based and non-linear models both predicted the sum of concentrations exactly. A 1% upper prediction bound and the non-linear model predicted the peak emission rate moderately well (64 to 92%, and 63 to 93%, respectively). Mean levels of indoor particulate matter measurements differ substantially from peak concentrations. The use of the mean is only sufficient to predict the sum of concentrations. We suggest that, mite aeroallergen measurements should include information on the peak as well as the mean

Reproducibility of questions on environment characteristics related to mite allergen load independent from education on environment

No abstract

Combined analysis of environmental characteristics affecting mite allergen load (Acari) in Dutch bedrooms (Abstract 28)

No abstract

Building measures against cockroaches

No abstrac

The abundance of house dust mites (Pyroglyphidae) in different home textiles in Europe, in relation to outdoor climates, heating and ventilation

In Europe, house dust mites of the family Pyroglyphidae are abundant producers of allergens in dwellings. Their prevalence in dwellings as well as their distribution among different types of home textiles vary in different localities in Europe. The main limiting factor for mite population growth is water activity. Water activity is closely related to relative humidity in the mite niche. Relative humidity in the mite niche is influenced by outdoor temperature and absolute air humidity, heating and ventilation. The mean January outdoor air temperature was determined. Based on outdoor temperatures and absolute air humidities, the length of heating season and length of mite population growth season for different home textiles were defined. These variables were validated with published data on mite abundance in mattresses and on floors in climatically distinct areas in Finland, Denmark, United Kingdom, The Netherlands, France, Switzerland, Italy and Poland. Length of mite population growth season - abbreviated to mite season - can be shortened by effective ventilation. Therefore, minimal required ventilation rates, to keep the relative humidity in the mite niche below the hygienic moisture limit for mite population growth, in European countries, were collected. No significant correlation was demonstrated between length of heating season and mite numbers in any of the home textiles. Between mean January outdoor air temperature and mite numbers in mattresses; and between length of mite season and mite numbers in mattresses, significant correlations were seen (Spearman rank correlation test, p <0.05). On floors, none of the climatic variables showed a significant correlation with mite numbers. Minimal required ventilation rates were found in Denmark and the Netherlands, only. In contrast to length of heating season, mean January outdoor air temperature and length of mite season in mattresses can predict the overall abundance of house dust mites in mattresses in a climatic area. To predict the overall mite burden on floors, the influence of outdoor climate should be examined in combination with soil and constructional factors. To shorten the length of the mite population growth season minimal required ventilation rates have to be known

The abundance of house dust mites (Pyroglyphidae) in different home textiles in Europe, in relation to outdoor climates, heating and ventilation

In Europe, house dust mites of the family Pyroglyphidae are abundant producers of allergens in dwellings. Their prevalence in dwellings as well as their distribution among different types of home textiles vary in different localities in Europe. The main limiting factor for mite population growth is water activity. Water activity is closely related to relative humidity in the mite niche. Relative humidity in the mite niche is influenced by outdoor temperature and absolute air humidity, heating and ventilation. The mean January outdoor air temperature was determined. Based on outdoor temperatures and absolute air humidities, the length of heating season and length of mite population growth season for different home textiles were defined. These variables were validated with published data on mite abundance in mattresses and on floors in climatically distinct areas in Finland, Denmark, United Kingdom, The Netherlands, France, Switzerland, Italy and Poland. Length of mite population growth season - abbreviated to mite season - can be shortened by effective ventilation. Therefore, minimal required ventilation rates, to keep the relative humidity in the mite niche below the hygienic moisture limit for mite population growth, in European countries, were collected. No significant correlation was demonstrated between length of heating season and mite numbers in any of the home textiles. Between mean January outdoor air temperature and mite numbers in mattresses; and between length of mite season and mite numbers in mattresses, significant correlations were seen (Spearman rank correlation test, p <0.05). On floors, none of the climatic variables showed a significant correlation with mite numbers. Minimal required ventilation rates were found in Denmark and the Netherlands, only. In contrast to length of heating season, mean January outdoor air temperature and length of mite season in mattresses can predict the overall abundance of house dust mites in mattresses in a climatic area. To predict the overall mite burden on floors, the influence of outdoor climate should be examined in combination with soil and constructional factors. To shorten the length of the mite population growth season minimal required ventilation rates have to be known