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Giornale Italiano di Dermatologia e Venereologia 2004 June;139(3):195-206


language: English, Italian

The atopy patch test with whole dust mite bodies at 20%. Evaluation of outcomes in adult atopic dermatitis, non-eczematous atopic patients and healthy subjects

Ingordo V.

Department of Dermatology “M.O. Giulio Venticinque”, Italian Navy Main Hospital Taranto, Italy


Aim. Based on the observation that a subgroup of patients reacted positively to the application of environmental aeroallergens on the skin, a patch test with these allergens has been proposed in the study of atopic dermatitis (AD). This test is named atopy patch test (APT) and the most employed allergens are house dust mites (HDM). The aim of this study is to investigate the reaction to APT, using a commercial extract of whole bodies of HDM at 20%, in patients with AD in comparison with non-eczematous atopic subjects and unaffected individuals.
Methods. Three groups of subjects were patch tested with a commercial extract, containing 20% purified mite bodies of HDM, comprising equal amounts of Dermatophagoides pteronyssinus and Dermatophagoides farinae, suspended in white petrolatum (60%) and petrolatum oil (20%). The groups tested were the following, selected randomly among the subjects attending our Department: 1) 74 patients affected by AD (73 males and 1 female), with a mean age of 20.7±2.6 years (min-max: 15-32 years) and a mean SCORAD index of 36±18.1 (min-max: 3.5-71.9), diagnosed according to the criteria of Hanifin and Rajka. Skin prick tests (SPT) with environmental aeroallergens were performed and the level of total circulating IgE was measured. All the AD patients were also patch tested with the Gruppo Italiano di Ricerca Dermatiti da Contatto e Ambientali (GIRDCA) standard series and, if required, with additional series, for diagnosing a coexisting allergic contact dermatitis; 2) 54 non-eczematous atopic male patients with mean age of 20.3±3.8 years (min-max: 18-32 years), and a negative anamnesis for any form of eczema. Twenty-seven patients had an allergic respiratory disease, 6 an acute or relapsing urticaria in the past and 20 did not have any symptom (latent atopic individuals or subjects with atopic state). They were selected by positivity to SPT for the same aeroallergens/foods tested in AD and/or by raised total serum IgE; 3) 52 non-atopic subjects, 50 males and 2 females, with mean age of 21.7±4.4 years (min-max: 18-42 years), negative anamnesis for any form of eczema and other allergic diseases, negativity of SPT for the aforesaid aeroallergens/foods and normal total serum IgE.
Results. APT was positive respectively in 51.35%, 31.48% and 10.34% of AD, non-eczematous atopic and non-atopic patients. The differences in outcome of APT between the AD, non-eczematous atopic and non-atopic groups were statistically significant and the trend was significantly negative from ADs to non-eczematous atopics and to non-atopics. The odds-ratios were also significant, showing a higher odds-ratio in ADs than in non-eczematous atopics and non-atopics (Cochran-Armitage Trend test). APT and SPT with Dermatophagoides spp. were concordant in both AD and non-eczematous atopic groups, but with a higher relative prevalence of the AD group. In the non-eczematous atopic group, APT was positive in 31.48% of subjects, a rate lower than that detected in the AD group (51.35%) with statistical significance. On the contrary, the difference in SPT-positivities between the two groups was not significant. Moreover, in the AD group APT and SPT were concordant, but the concordance was not absolute. In fact, 14 patients (18.92%) were APT-negative/SPT-positive and 7 patients (9.45%) were APT-positive/SPT-negative. In the AD group, also, no significant difference in mean values of IgE/SCORAD index and in increased/normal levels of total IgE between the APT-positive and APT-negative subgroups was shown. No statistically significant difference was detected in APT outcome between the different age-onset groups of AD (Infancy-onset, Childhood-onset, Adolescence-onset and Adult-onset). No statistically significant difference in APT outcome between the air-exposed pattern and non air-exposed pattern of eczema was shown.
Conclusion. According to our data, one could conclude that APT with HDM is positive in a high proportion of adult AD, and its outcome is not related to severity, clinical pattern or length of disease. It also seems to be unrelated strictly to the presence of HDM-specific circulating IgE. APT-positivity seems to be more specific than SPT for AD, but a small percentage of non-eczematous atopic and non-atopic individuals also react to testing. Therefore further experience, carried out on larger series, selecting pediatric and female patients as well, using purified, more standardized HDM extracts with different concentrations, is needed to confirm our data.

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