Study of the effects of vacuuming on the concentration of dust mite antigen and endotoxin

Background: Dust mite antigens are major sources of allergens in house dust and together with endotoxin, a proinflammatory component of gram negative bacteria also found in house dust, are important causes of tissue injury invoked in the pathogenesis and severity of allergic diseases, eg, asthma. Objective: To determine the effectiveness of vacuuming in reducing the quantity of dust mite antigens, Dermatophagoides pteronyssinus (Der p1 and Der p2) and endotoxin using a quantitative ELISA assay and to correlate results with those obtained using a qualitative rapid dipstick method for Der p2. Methods: Four specimens of house dust were collected using a Kirby Model G5 vacuum cleaner with a Micron Magic Filtration system from an approximately 54 " x 18 " standardized area of rug from each of 20 homes at 4 time intervals over a 6-week period, ie, a baseline specimen #1 at 0 week; specimen #2 at 1 week; specimen #3 at 5 weeks (1 month after specimen #2); specimen #4 at 6 weeks (1 week after specimen #3). Three intervals were compared, ie, period 1-2 (1 week), period 2-3 (1 month), and period 3 to 4 (1 week). The concentrations of Der p1 and Der p2 were determined in dust samples using a standard ELISA assay and the concentration of endotoxin was detected using a limulus amebocyte lysate assay. Concentrations of Der p2, determined by the standard ELISA assay, were compared to those in the same samples determined by a rapid dipstick method. Results: A wide range of values for total weight of unprocessed dust (0.3 to 59 g, (X) over bar = 8.7) and finely sieved dust (0.1 to 19 g, (X) over bar = 3) from all specimens were found. In finely sieved dust specimens the mean concentrations of Der p1, Der p2 and endotoxin were 775, 1310, and 3836 ng/g of dust, respectively. Following weekly vacuuming there was an increase in concentration of Der p1, Der p2, and endotoxin in 20%, 35%, and 63% of the houses, respectively, compared to in monthly vacuuming in which increases were seen in 65%, 50%, and 63% of the houses, respectively. in contrast, there was a decrease in concentration of Der p1, Der p2 and endotoxin with weekly vacuuming in 43%, 60%, and 37% of the houses respectively versus in monthly vacuuming in 15%, 35%, and 37% of the houses respectively. A correlation coefficient of 0.7 was found for the concentration of Der p2 in 37/40 samples tested detected using the ELISA method compared with rapid dipstick assay. Conclusion: The results of this study support the effectiveness of vacuuming on the reduction of dust mite antigens (Der p1 and Der p2) ie, Der p2> Der p1. This reduction was more pronounced with weekly compared with monthly vacuuming. No reduction in the concentration of endotoxin was found. A good correlation was found between results obtained by ELISA and rapid dipstick assay for Der p2.