Study Of Atopy Patch Test In The Diagnosis Of Allergy To Common Allergens In Atopic Dermatitis

ObjectiveTo evaluate the clinical significance and the diagnostic accuracy of atopy patch test (APT) for the most common aeroallergens and food allergens in patients with atopic dermatitis (AD).MethodsSeventy-nine AD subjects (aged from 3 to 29) were enrolled in the study of atopy patch test with aeroallergens (Der.p, Der.f, cat dander, dog dander and platanus pollen), and food allergens (egg,milk,soybean.wheat and prawn). All subjects were also tested with skin-prick test (SPT) and specific serum IgE in comparison with APT to evaluate its sensitivity and specificity. At the same time to further analyze the result of APT for Der.p and Der.f in correlation with AD's clinical phenotype and disease prevalence.ResultsAPT with Der.p and Der.f extracts showed highest positivity (25.3%,29.1%) compared to other common aeroallergens (cat dander13.9%, dog dander 15.2%, platnus pollen 8.9%). Soybean was 26.7% higher than other food allergens (egg23.7%, milk 23.4%, prawn23.1%, wheat16.0%). Using the "slgE level" as a gold standard, the specificity of APT with aeroallergens was slightly higher (85.2%-92.6%) whereas the sensitivity was lower(11.1%-32.3%). The positive predictive value (ppv) of APT with Der.p and Der.f extracts were both high (95.0%,91.3%). There was no statistic correlation between APT and AD patients with their history of allergic rhinitis. The positive results of APT between 'intrinsic' and 'extrinsic' subgroups of AD did not show statistic significance. APT with increased protein concentration of Der.p showed a parallel increase in positivity. Moreover, Der.p extracts with petrolatum plus emulsifier showed higher positivity (54.2%) than APT using just petrolatum alone (25.3%), and this difference was statistically significant. The positivity of Der.f APT using petrolatum plus emulsifier also increased comapring to using just petrolatum, the difference however, was not significant.ConclusionsMite was one of the most common aeroallergens in AD patients. The specificity of APT was a little bit higher and the ppv of APT with mite allergens was more than 90%. There was no significant correlation between APT results and AD patients with the history of allergic rhinitis, nor was there a significant difference between 'intrinsic' and 'extrinsic' subgroups of AD. There was no statistic relevance between the positive results of APT and the level of skin dryness. Both use of emulsifying agent into petrolatum mixtures and inceasing concentration of mite allergens induced more positive results.