December 12th, 2017
To evaluate the effects of nonpolyurethane house dust mite (HDM)-impermeable covers (for mattresses, duvets and pillows) on the peak expiratory flow (PEF) and symptom scores of asthmatic patients (aged 12-60 years) with HDM allergy from Netherlands [date not given], subjects were randomly allocated to the allergen-avoidance group (n=26; use of HDM-impermeable covers) or the control group (n=26; use of HDM-permeable covers). Dust samples were taken from mattresses at the beginning of the 2-week baseline period, one week after the start of the 9-week intervention period, and at the end of the intervention period to determine the presence of Dermatophagoides pteronyssinus group 1 allergen (Der p 1). The symptom scores evaluated included cough, breathlessness, wheezing, expectoration, tiredness, and disturbed sleep. No variable differed significantly between the 2 groups. One control patient was not analysed for clinical parameters due to lack of data. The levels of HDM allergens and total dust were significantly lower in the avoidance group than in the control group after one week of the intervention. Der p 1 (in µg/m) and total dust levels remained significantly lower in the avoidance group than in the control group after 9 weeks of the intervention. Reductions in Der p 1 level of 98.5% and 95.4% (both P=0.001) were found in the avoidance group after one and 9 weeks of intervention, respectively. Because the baseline symptom score was very low in the study population, no analysis was done on the effect of HDM avoidance on symptom score. The average morning PEF was significantly higher in the avoidance group than in the control group during 9 weeks of follow-up (P=0.01). It is concluded that the use of HDM-impermeable covers reduces the exposure of asthmatic patients to house dust and Der p 1, and improves their morning PEF.