VARIABILITY OF HOUSE-DUST MITE ALLERGEN EXPOSURE IN DWELLINGS

The variability of repeated house dust mite (HDM) allergen determinati ons at the same site within 3-24 months was evaluated on previously co llected samples. Between two and four repeated measurements of Der p 1 , a major allergen of Dermatophagoides pteronyssinus and Der f 1, a ma jor allergen of D. farinae, on 46 carpets and 31 mattresses were analy zed. In 30% of carpets and mattresses, HDM allergen concentrations wer e clinically relevant (at least one measurement >0.1 mu g Der p 1 + De r f 1/g dust). The coefficients of variation (CVs) for allergen concen trations in repeated samples over time (55.3-82.0% for the two allerge ns in beds and carpets) were dearly greater than the CVs for multiple samples collected at the same time (4.0-32.6%). Determination of aller gen 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 sin gle determination. We conclude that single determinations of HDM aller gen 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 w ith appropriate sample sizes.