Variability of House Dust Mite Allergen Exposure in Dwellings

Abstract

Tlhe variability of repeated house dust mite (HDM) allergen determinations at the same site within 3-24 months was evaluated on previously collected samples. Between two and four repeated measurements of Der p 1, a major allergen of Dermatophagoidespteronyssinus and Der f 1, a major allergen of D. farinae, on 46 carpets and 31 mattresses were analyzed. In 90% of carpets and mattresses, HDM allergen concentrations were cinically relevant (at least one measurement >0.1 pg Der p 1 + Der f l/g dust). The coefficients ofvariation (CVs) for allergen concentrations in repeated samples over time (55.3-82.0% for the two allergens in beds and carpets) were clearly greater than the CVs for multiple samples collected at the same time (4.0-32.6%). Determination ofallergen mass per square meter of surface instead of concentration per gram of dust resulted in an even greater CV (72.3-86.7%). The 95% range of expected values was about 10-fold above and below the result of a single determination. We conclude that single determi-nations of HDM allergen in dust give very limited information about long-term exposure of an individual to the allergen. Repeated measurements are recommended. Studies of factors that affect HDM allergen exposure must be planned with appropriate sample sizes. Key words: asthma , house dust mite allergens, indoor allergen eTosure, reliability, repeated determination, sample size, yariability. Environ Health Perspect 106:659-664 (1998). [Online 11 September 1998] hbfp://ehpnetl.niehs.nih.gov/does/998/106p659-664birshlabstract.hbtmI Some studies have shown that exposure to house dust mite (HDM) allergens at home is associated with prevalence of allergic sensitiza-tion (1-3) and asthma (4,5) in susceptible children, but others did not (6,7). The reliability of the determination of indoor exposure to these allergens has not been investigated extensively. Marks and co-workers (8) calculated that threefold above and below a result was the range within which the true value lies with 95% certainty. The authors referred to 117 duplicate determinations of Der p 1, a major allergen of Dermatophagoides pteronyssi-nus, within 2 weeks in Sydney, Australia. In contrast to most other parts of the world (2,3,6,5), Sydney is characterized by extremely high concentrations of Der p 1 [geometric mean 38.9 pg/g dust on mattresses and 22.4 pg/g dust on bedroom floors (8)] and the absence of other HDM allergens. Two recent studies have shown that the prevalence of allergic sensitization in children correlates with exposure to HDM allergen at concentrations far below these levels [0.1 pg Der p 1 + Der f 1 (a major allergen of D. faninae)lg carpet dust (3) or even lower (2]. Thus, it seems reasonable to compare the Australian results with data from a European region with low to moderate levels of Der p 1 and, in addition, moderate concentrations of the HDM allergen Der f 1 to answer two questions: 1) Is the (relative) variability of allergen concentration higher at lower exposure levels? 2) Is the variability of Der f 1 exposure lo...

Reproducibility of allergen, endotoxin and fungi measurements in the indoor environment

“…Repeated measurements of Der p 1 and Der f 1 in 91 children's mattress dust showed generally higher correlations (0.76-0.95) compared with this study on floor dust measurements, but the reported correlation coefficient for Der f 1 was consistent with our study and higher than Der p 1 correlation (Peterson et al, 1999). Another study in Germany by Hirsch et al (1998) showed only a weak correlation between two and four repeated measurements of Der p 1 and Der f 1 on carpets (n ¼ 46) and mattresses (n ¼ 31). The authors concluded that single observations of dust mite allergens in house dust give only limited information about long-term exposure.…”

“…Allergen concentration and total mold spore counts The seasonal variation of allergen and mold concentrations in different climates has been discussed in detail in the literature, indicating allergen-specific seasonalities (Platts-Mills et al, 1987;Lintner and Brame, 1993;Munir et al, 1993;ChanYeung et al, 1995;Marks et al, 1995;Miyazawa and Suzuki, 1996;Hirsch et al, 1998;Koch et al, 2000;Chew et al, 2001;Su et al, 2001).…”

“…Thus, exposure assessment may be further improved by considering variability over time, including seasonal effects on indoor biocontaminant levels. Studies on repeated measurements of mite allergens in house dust samples consistently showed a correlation between repeated measurements (Kuehr et al, 1994;Marks et al, 1995;Hirsch et al, 1998;Petersen et al, 1999). However, different conclusions were drawn from those studies.…”

“…However, different conclusions were drawn from those studies. Some authors (Hirsch et al, 1998;Petersen et al, 1999) conclude that repeated measure-ments are recommended, whereas others (Kuehr et al, 1994) concluded that allergen levels are relatively stable. Chew et al (2001) studied fungal extracellular polysaccharides (EPS), b (1,3)-glucans and culturable fungi in house dust that was sampled at six occasions in 23 Dutch homes during a period of 1 year.…”

Effects of physical interventions on house dust mite allergen levels in carpet, bed, and upholstery dust in low-income, urban homes.

“…Indeed, it is well established that HDM allergen levels can vary over time and during different seasons (32,33). We observed a 4-to 8-fold reduction in pretreatment allergen concentrations after interventions in homes enrolled between July-March and followed for 8 weeks.…”