R.T. van Strien

Mite antigen in house dust: relationship with different housing characteristics in the Netherlands.

As part of a case‐controlled study on the relationship between home dampness and respiratory symptoms of children, the concentration of the major allergen of Dermato‐phagoides pteronyssinus (Der p I) in floor dust and mattress dust in 516 dwellings in the Netherlands was measured. A checklist, completed by the investigators, was used to obtain information on home and occupant characteristics, which may have an impact on the Der p I concentration in house dust. The geometric mean mite antigen concentrations were 2370 ng Der p I/g floor dust for the living room, 2201 ng Der p I/g floor dust for the bedroom and 5075 ng Der p I/g mattress dust. In 86% of the houses the maximum concentration was higher than 2000 ng Der p I/g dust, that is regarded as representing a risk for genetically predisposed individuals for the development of specific IgE to house dust mite allergen. In 55% of the houses the maximum concentration exceeded 10000 ng Der p I/g dust, regarded as a risk factor for acute attacks of asthma for mite allergic patients. The Der p I concentrations in dust from carpeted floors were six to 14 times higher than in dust from floors with a smooth floor covering. Higher Der p I concentrations in floor dust were also significantly associated with increasing age of the dwelling and of the floor covering, with an increasing number of occupants, and with the absence of floor insulation. For mattress dust, the age of the mattress, the presence of an outer cavity wall and mechanical ventilation were important factors. Older mattresses had higher levels, and mattress dust from bedrooms with solid brick outer walls had higher levels than that from bedrooms with outer cavity walls. Mattresses in homes with continuous mechanical ventilation had almost twice lower levels than mattresses in homes with natural ventilation. There was a tendency towards higher Der p I concentrations in dust in homes with reported or observed signs of dampness. The Der p I concentrations in dust from carpeted bedroom floors and mattresses were positively associated with the average relative humidity in the bedroom over a period of 3–6 weeks in a subset of the homes where relative humidity was measured. Similar results were obtained using the concentrations of Der p I in ng/m2 instead of ng/g dust. The results obtained in this study are of importance for planning and evaluating allergen avoidance measures advised to mite allergic patients.

Validation of a screening questionnaire for atopy with serum IgE tests in a population of pregnant Dutch women

We have started a large birth cohort study in which pregnant women with and without atopy are differentially included. In view of the large number of subjects to be screened (12 000), a simple questionnaire was developed for the assessment of atopy in pregnant women.

Risk factors for atopic dermatitis in infants at high risk of allergy: the PIAMA study

Background It has been suggested that the period immediately after birth is a sensitive period for the development of atopic disease.

Fungal propagules in house dust. II: Relation with residential characteristics and respiratory symptoms

As part of a case‐control study on the relation between home dampness and respiratory symptoms of children, house‐dust samples were collected from bedroom floors and mattresses in 60 homes in The Netherlands. The house‐dust samples were analyzed for the presence of fungal propagules by plating 30 mg of dust directly onto DG18 agar. A checklist and questionnaire were used to obtain information on the home characteristics and occupant behavior that may have an effect on the presence of fungal propagules in house dust. The geometric mean (GM) number of colony‐forming units (CFU)/g dust collected from the floors was 8990. The number of CFU/g dust was significantly higher in dust from carpeted floors than in dust from smooth floors (GM, respectively, 12880 CFU/g dust and 3530 CFU/g dust). The GM number of CFU/g dust collected from mattresses was 6760. Overall, the mean numbers of CFU/g dust collected from floors and mattresses were higher in bedrooms where damp spots mold growth, or both were observed. However, these differences were not statistically significant. The relation between home characteristics and the number of CFU/g dust of the most frequently isolated mold species (n= 17), including Alternaria alternata, Cladosporium cladosporioides, Penicillium brevicompactum, and Scopulariopsis brevicaulis, was also investigated. Only the type of flooring had a significant and consistent effect on the number of CFU/g floor dust of the different mold species. For P. brevicompactum, the number of CFU/g floor dust was significantly higher in bedrooms where damp spots were observed. The number of CFU/g mattress dust of S. brevicaulis was also significantly higher for bedrooms where damp spots were observed. However, in view of the large number of statistical comparisons made, these two significant relationships might have been caused by chance alone. The total numbers of CFU/g mattress and floor dust were not related to the average relative indoor humidity measured over 6 weeks. Furthermore, there was no association between the presence of fungi in house dust and respiratory symptoms. We conclude that there was only a very weak relationship between the home characteristics and occupant behavior, as determined by checklist and questionnaire, and the presence of fungal propagules in floor dust and mattress dust. Only the type of flooring had a substantial and statistically significant effect on the presence of fungal propagules in floor dust. Therefore, the presence of fungal propagules in house dust cannot be predicted reliably by home characteristics.

Mattress encasings and mite allergen levels in the Prevention and Incidence of Asthma and Mite Allergy study

Background Reduction of allergen exposure from birth may reduce sensitization and subsequent allergic disease.

Using nicotine measurements and parental reports to assess indoor air: The PIAMA birth cohort study

We used two methods to collect data on indoor smoking exposure of 3-month-old infants. First, parents of approximately 100 children completed a questionnaire. We then measured nicotine in the air of the living rooms in smoking and non-smoking households with a passive sampler for a period of 2 weeks, several months after the questionnaire had been completed. Smoking habits reported in the questionnaire generally with reported number of cigarettes smoked during the measurement weeks, and with nicotine concentrations in the air. These results suggest that exposure classification based on questionnaire data is likely to be reasonably valid.

The 8-year follow-up of the PIAMA intervention study assessing the effect of mite-impermeable mattress covers

To cite this article: Gehring U, de Jongste JC, Kerkhof M, Oldewening M, Postma D, van Strien RT, Wijga AH, Willers SM, Wolse A, Gerritsen J, Smit HA, Brunekreef B. The 8‐year follow‐up of the PIAMA intervention study assessing the effect of mite‐impermeable mattress covers. Allergy 2012; 67: 248–256.

Der p I concentrations in mattress surface and floor dust collected from infants' bedrooms.

Background Allergen exposure in early childhood is thought to be important for sensitization and subsequent development of asthma. Not much is known, however, about exposure of young children to allergens in the home.

House dust mite allergen (Der p I) and respiratory symptoms in children: a case‐control study

The association between house dust mite allergen in house dust and childhood respiratory symptoms was investigated in a case‐control study of 259 children with reported chronic respiratory symptoms and 257 control children without reported respiratory symptoms. The Der p I concentration in floor dust of the living room and bedroom and in mattress dust was determined using an enzyme immunoassay. Venous blood samples were taken from all children for serum IgE determination against house dust mite (Dermatophagoides pteronyssinus) by radioallergosorbent assay (RAST). A questionnaire was administered to the parents of the children to elicit information about the home, about changes made to the home in the past in relation to respiratory symptoms, and about a number of risk factors for childhood respiratory disease. In 83% of the dwellings of cases and 89% of those of controls, Der p I concentrations higher than 2000 ng/g were found, and in 54% of the dwellings of cases and 57% of those of controls, the concentrations exceeded 10 000 ng/g dust. In a crude analysis, cases were generally exposed to lower Der p I concentrations than controls. Restriction of the analysis to cases sensitized to dust mites, and non‐sensitized controls, taking the type of floor covering into account, showed not significantly higher Der p I concentrations in bedroom floor dust of cases. However, restriction of the analysis to cases sensitizied to dust mites and cases not sensitized to house dust mites — adjusting for allergen avoidance measures taken in the past — revealed a positive association between the Der p I concentrations in bedroom floor dust and mattress dust and sensitization. This finding indicates that allergen avoidance measures modify current exposure to Der p I. This obscures the relationship between the exposure to mite allergens and sensitization, and hampers the estimation of the association between exposure to house dust mite allergens, sensitization and the development of respiratory symptoms.

Early respiratory and skin symptoms in relation to ethnic background: The importance of socioeconomic status; the PIAMA study

Aims: To evaluate ethnic differences in the prevalence of respiratory and skin symptoms in the first two years of life. Methods: A total of 4146 children participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study. Parents completed questionnaires on respiratory and skin symptoms, ethnic background, and other potential confounders during pregnancy, and at 3 months, 1 year, and 2 years of age. Results: In the first year, “non-Dutch” children (compared with “Dutch” children) had a higher prevalence of runny nose with itchy/watery eyes (11.0% versus 5.0%). In the second year, a higher prevalence of wheeze at least once (26.7% versus 18.5%), night cough without a cold (24.6% versus 15.5%), runny nose without a cold (34.1% versus 21.3%), and runny nose with itchy/watery eyes (13.7% versus 4.6%) was found. Adjustment for various confounders, especially adjustment for socioeconomic factors, reduced most associations between ethnicity and respiratory symptoms. Only runny nose with itchy/watery eyes in the second year of life was independently associated with non-Dutch ethnicity (adjusted odds ratio 2.89, 95% CI 1.3–6.4). Conclusions: Non-Dutch children more often had respiratory symptoms in the first two years of life than Dutch children. This could largely be explained by differences in socioeconomic status. Follow up of the cohort will determine whether this higher prevalence of respiratory symptoms in children with non-Dutch ethnicity represents an increased risk of developing allergic disease rather than non-specific or infection related respiratory symptoms.