Is the Atopy Patch Test with House Dust Mites Specific for Atopic Dermatitis?

Abstract

Background: The atopy patch test (APT), namely the patch test with aeroallergens, is regarded as specific for patients with atopic dermatitis (AD), but small numbers of positive APT were reported in the past also in atopic subjects without dermatitis and in healthy persons. Objective: The aim of this study was to evaluate the response to the APT with house dust mites (HDM) in subjects nonaffected by AD and to compare the outcomes observed in these cases with those pointed out in AD patients, evaluating also the differences between two allergen extracts manufactured at different purifications and concentrations. Methods: Forty-seven atopic subjects without eczema (AWE), 33 nonatopic (NA) subjects and 77 adult AD patients were patch tested with an extract of purified bodies of HDM at 20% and with another extract of whole bodies of HDM at 30%, the latter corresponding to 300 µg/g of Der p 1. The reproducibility of APT was also tested in 8 AD patients, in 37 AWE subjects and in 19 NA subjects. Results: Positive responses with extract at 20% were observed in 29 (37.7%) AD, in 5 (10.6%) AWE and in 4 (12.1%) NA subjects. The APT with HDM at 30% was positive in 32 (41.6%) AD, 9 (19.1%) AWE and 4 (12.1%) NA persons. The rates of positivity and the intensity scores of responses were significantly different between AD and non-AD subjects (p < 0.01). The reproducibility of the APT in the three groups was satisfactory. Conclusion: These observations lead to conclude that the APT with HDM is positive also in non-AD subjects but it is probably more specific for AD.

Epidemiology of atopy patch tests with food and inhalant allergens in an unselected population of children

“…This statement, supported by the results of some studies, has never been clearly addressed or contradicted by an experiment designed specifically to test it. However, several reports including groups of healthy controls or atopic patients without eczema show a considerable percentage of positive APTs in non‐eczematous patients (19–20). Existing data suggest that the prevalence of positive APTs in children selected for suspected food allergy is higher in those with positive food challenges than in those with negative food challenges (9, 19, 21, 22).…”

“…However, several reports including groups of healthy controls or atopic patients without eczema show a considerable percentage of positive APTs in non‐eczematous patients (19–20). Existing data suggest that the prevalence of positive APTs in children selected for suspected food allergy is higher in those with positive food challenges than in those with negative food challenges (9, 19, 21, 22). In general, in healthy or symptomatic subjects, APT results differ widely among tested allergens (naive or standardized food) and depend closely on technical variables (e.g.…”

Reproducibility of food atopy patch tests over time in the general child population

“…Using inhalant allergens from two different commercial sources, two sites of application (back and arms), and results in eczematous and healthy subjects retested after two to several weeks, Bygum et al 8 . and Ingordo et al 12 . reported an APT reproducibility of less than 70%, which corresponds to a Cohen's κ value of 0.60–0.85 (satisfactory to highly satisfactory agreement).…”

The role of atopy patch tests in the diagnosis of allergy in atopic dermatitis

“…Ingordo et al [7] confirmed a satisfactory repeatability with two different HDM extracts in eight patients with atopic dermatitis, 37 atopic patients without eczema and 19 atopic patients [7]. Ingordo et al [7] confirmed a satisfactory repeatability with two different HDM extracts in eight patients with atopic dermatitis, 37 atopic patients without eczema and 19 atopic patients [7].…”

“…Ingordo et al [7] performed APTs with house dust mite (HDM) extracts (extract of purified bodies of HDM at 20% and with another extract of whole bodies of HDM at 30%, the latter corresponding to 300 mg/g Der p 1.) Ingordo et al [7] performed APTs with house dust mite (HDM) extracts (extract of purified bodies of HDM at 20% and with another extract of whole bodies of HDM at 30%, the latter corresponding to 300 mg/g Der p 1.)…”