PREDICTION OF MITE ALLERGEN LEVELS BY GUANINE MEASUREMENTS IN HOUSE-DUST SAMPLES

We studied the sensitivity and specificity of guanine environmental te sts in the evaluation of the two mite allergen levels, i.e. 2 mug/g an d 10 mug/g of Der p I and Der f I, considered to be risk factors for s ensitization or for the development of acute asthma. We examined 239 h ouse-dust samples for Der p I and Der f I levels (ELISA) and guanine c ontents (semiquantitative guanine test and quantitative assays). All h ouse-dust samples with class 2 or 3 guanine tests contained more than 2 mug/g of Der p I and Der f I. The probability that house-dust sample s of class 2 contained more than 10 mug/g of mite allergens was 88%; i t was 100% for house-dust samples of class 3. The probability that a h ouse-dust sample of class 0 contained less than 2 mug/g of mite allerg en was 87%. For each level of mite allergen, a ROC curve was construct ed with the true positive rates and the false positive rates calculate d by different cutoffs of guanine concentration. The cutoff point whic h gave the best compromise between sensitivity (76%) and specificity ( 89%) was 2100 mug/g for the threshold of 2 mug/g of Der p I and Der f I. For detection of a mite allergen > 10 mug, a guanine content of 300 0 mug/g gave the best compromise between sensitivity (86%) and specifi city (93%). In conclusion, the guanine test represents a satisfactory environmental test, inexpensive and simple, for predicting mite allerg en levels. Semiquantitative and quantitative guanine measurements are more accurate in predicting an exposure level of 10 mug/g than of the level 2 mug/g of Der p I and Der f I.