| Variability of House Dust Mite Allergen Exposure in Dwellings Thomas Hirsch,1 Eberhard Kuhlisch,2 Wolfgang Soldan,1 and Wolfgang Leupold1 1Children's Clinic and 2Institute for Medical Informatics and Biostatistics, University Hospital, Dresden, Germany Abstract
The 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 Dermatophagoides pteronyssinus 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 clinically relevant (at least one measurement >0.1 µg Der p 1 + Der f 1/g dust) . The coefficients of variation (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 of allergen 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 determinations 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 exposure, reliability, repeated determination, sample size, variability. Environ Health Perspect 106:659-664 (1998) . [Online 11 September 1998] http://ehpnet1.niehs.nih.gov/docs/1998/106p659-664hirsch/ abstract.html Address correspondence to T. Hirsch, Kinderklinik des Universitatsklinikums Carl Gustav Carus der Technischen Universitat Dresden, Fetscherstr. 74, D-01307 Dresden, Germany. We thank Ursula Schulz, Christa Sproessig, Margret Saehn, and Gertraud Karge for their commitment and cooperation. This study was supported by the State of Saxony, Germany, through a governmental research fund. Received 30 December 1997 ; accepted 3 June 1998.
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