Is the atopy patch test with house dust mites specific for atopic dermatitis?
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 microg/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.


CONCLUSIONS
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.
Ingordo
Vito
V
Department of Dermatology, Italian Navy Main Hospital MO Giulio Venticinque, Taranto. vitoingo@tin.it
Dalle Nogare
Roberto
R
Colecchia
Bruno
B
D'Andria
Corrado
C
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D000818:Animals; D016022:Case-Control Studies; D003876:Dermatitis, Atopic / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008925:Mites / Q000276:immunology*; D010328:Patch Tests / Q000379:methods*; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
D000485:Allergens