Atopy patch testing--a diagnostic tool?

Departmentof Pharmacology, University of Bern, Bern, SwitzerlandKey words: atopic dermatitis; clinical features;constitutional dermatitis; epidemiology; extrinsictype; immunopathology; intrinsic type.Prof. Dr B. Wu¨thrichAllergy Unit, Department of DermatologyUniversity Hospital8091 ZurichSwitzerlandAccepted for publication 22 March 2001

The atopy patch test (APT) was proposed to evaluate IgE-mediated sensitizations in patients with atopic eczema (AE). The prevalence and agreement with clinical history and specific IgE (sIgE) of positive APT reactions was investigated in six European countries using a standardized method. A total of 314 patients with AE in remission were tested in 12 study centers on clinically uninvolved, non-abraded back skin with 200 index of reactivity (IR)/g of house dust mite Dermatophagoides pteronyssinus, cat dander, grass, and birch pollen allergen extracts with defined major allergen contents in petrolatum. Extracts of egg white, celery and wheat flour with defined protein content were also patch tested. APT values were evaluated at 24, 48, and 72 h according to the European Task Force on Atopic Dermatitis (ETFAD) guidelines. In addition, skin-prick test (SPT) and sIgE and a detailed history on allergen-induced eczema flares were obtained. Previous eczema flares, after contact with specific allergens, were reported in 1% (celery) to 34% (D. pteronyssinus) of patients. The frequency of clear-cut positive APT reactions ranged from 39% with D. pteronyssinus to 9% with celery. All ETFAD intensities occured after 48 and 72 h. Positive SPT (16-57%) and elevated sIgE (19-59%) results were more frequent. Clear-cut positive APT with all SPT and sIgE testing negative was seen in 7% of the patients, whereas a positive APT without SPT or sIgE for the respective allergen was seen in 17% of the patients. APT, SPT and sIgE results showed significant agreement with history for grass pollen and egg white (two-sided Pr > /Z/ < or = 0.01). In addition, SPT and sIgE showed significant agreement with history for the other aeroallergens. With regard to clinical history, the APT had a higher specificity (64-91% depending on the allergen) than SPT (50-85%) or sIgE (52-85%). Positive APT were associated with longer duration of eczema flares and showed regional differences. In 10 non-atopic controls, no positive APT reaction was seen. Aeroallergens and food allergens are able to elicit eczematous skin reactions after epicutaneous application. As no gold standard for aeroallergen provocation in AE exists, the relevance of aeroallergens for AE flares may be evaluated by APT in addition to SPT and sIgE. The data may contribute to the international standardization of the APT.

The atopy patch test (APT) has been defined as an important tool in the diagnosis of cutaneous hypersensitivity caused by house dust mites in atopic dermatitis (AD). The aim of this study was to evaluate the diagnostic value of the APT to mite allergens by comparing its positive results with those of the skin prick test (SPT) and serum specific IgE test in Chinese AD patients. The APT, SPT and serum specific IgE test with Dermatophagoiodes pteronyssinus and Dermatophagoides farina were performed on a total of 120 patients with atopic dermatitis. Overall, 37.5% of the patients showed a positive APT reaction to mite allergens. A statistically significant association was observed between positive APT results and air-exposed eczema pattern. The positive APT results were not significantly associated with SCORAD scores and accompanied atopic respiratory disorders in AD patients. A higher frequency of APT positive reactions to mite allergens was observed in adolescent and adult patients. There was no significant difference in APT positivity between extrinsic patients (40.7%) and intrinsic patients (27.6%). This study identified house dust mite induced cutaneous hypersensitivity in Chinese patients with AD by APT, especially in air-exposed distribution patterns or adolescent and adult patients. Both intrinsic and extrinsic AD patients showed positive APT reactions to house dust mite.

Positive Atopy Patch Test Reaction to Malassezia furfur in Atopic Dermatitis Correlates with a T Helper 2-like Peripheral Blood Mononuclear Cells Response

The clinical usefulness of the atopy patch test (APT) is unclear for investigating aeroallergen- and food-triggered atopic dermatitis (AD). This study aimed to assess the prevalence of positive APT reactions in a population of adolescents and investigate possible associations between the APT, specific serum (s) immunoglobulin E (IgE) tests, self-reported atopic conditions and health-related quality of life. A population-based study was performed on 211 adolescents (13-14 years old). Collected data included questionnaires, an APT with food and aeroallergens and s-IgE tests. Positive APT reactions were observed in 9.0% (19/211) of the adolescents. Timothy grass was the top allergen with 11 (5.2%) positive reactions, followed by cat dander (2.8%) and house dust mites (2.4%). Rhinoconjunctivitis increased the odds of any positive APT (crude odds ratio: 3.32; 95% confidence interval [CI]: 1.17–9.40), particularly when an APT was positive for aeroallergens (odds ratio: 5.02, 95% CI: 1.54-16.42). There was no association between a positive APT and AD. Four adolescents without AD and no IgE-sensitization had a positive APT. Based on a population of adolescents, the APT is associated with rhinoconjunctivitis but not AD. This finding should be taken into consideration in further attempts to clarify the role of the APT in the clinical setting.

The atopy patch test (APT) is a procedure involving epicutaneous patch tests with allergens known to elicit IgE-mediated reactions and the evaluation of eczematous skin lesions. APT can be performed on normal uninvolved skin without artificial manipulations such as tape stripping or use of irritants. APT has been standardized regarding the use of vehicle and dose response relationships. In several studies, approximately two thirds of patients with atopic eczema (AE) showed positive APT reactions to aeroallergens, most frequently to house dust mite. Positive APT reactions were significantly more frequent in patients with a typical air-exposed eczematous distribution pattern. Using evaporimetry to study transepidermal water loss, allergen-induced disturbance of epidermal barrier functions was found to be significantly more pronounced on APT reactions compared to classical contact allergy patch test sites in the same individual. It has been shown that with APT eczematous skin lesions can be elicited by skin contact with aeroallergens, at least in a subgroup of patients with AE, and thereby, that IgE-mediated allergy does play a role in the etiopathophysiology of this disease. Future studies should help to bring this test into clinical routine in order to establish an equivalent for 'skin provocation' comparable to nasal and bronchial provocation tests in respiratory allergy.

Influence of Age on the Outcome of the Atopy Patch Test with Food in Children with Atopic Dermatitis

Atopic eczema (AE) is a common skin disorder. Eczematous lesions showing macroscopic, microscopic and immunopathological resemblance to lesional AE can be induced by aeroallergens by epicutaneous testing (atopy patch test, APT). Altered epidermal barrier function, as determined by transepidermal water loss (TEWL), is a typical feature of patients with AE. The present investigation was performed to define the differences in the epidermal barrier function between positive APT reactions to aeroallergens and positive patch test reactions to contact allergens in AE patients. Allergen extracts from grass pollen, birch pollen, cat dander and house dust mite (Dermatophagoides pteronyssinus) were applied in large Finn chambers on Scanpor for 48 h on the clinically unaffected and untreated skin of the back, in 11 patients with AE. The same procedure was done with 27 contact allergens of a standard test battery. Test reactions were read and TEWL was measured after 48 and 72 h. Eight of the 11 patients developed positive APT reactions to D. pteronyssinus, two to cat dander and one to birch pollen. Seven of the 11 patients showed positive patch test reactions to nickel sulphate, two to potassium dichromate, one to thiuram-mix and one to paraphenylenediamine. Vehicle controls were negative. The TEWL of the positive APT reactions was significantly higher, both after 48 h (mean +/- standard deviation 10.0 +/- 6.5 g/m2h) and after 72 h (9.7 +/- 5.4 g/m2h) as compared with the control site (48/72h: 4.4 +/- 1.5/4.1 +/- 1.4 g/m2h) (P < 0.01). In contrast, TEWL of the positive patch test reactions to contact allergens (48/72 h: 5.4 +/- 2.2/5.4 +/- 1.9 g/m2h) was similar to that of the control site (48/72 h: 5.2 +/- 2.1/5.0 +/- 1.8 g/m2h) (not significant). The relative TEWL at 48 h and 72 h, expressed as the ratio between the positive patch test and the control site, was significantly higher in the positive APT reactions (48/72 h: 218.8 +/- 80.4%/232.0 +/- 85.9%) compared with positive patch test reactions to contact allergens (48/72 h: 102.1 +/- 12.0%/107.1 +/- 9.5%) (P < 0.01). It is concluded that the epidermal barrier function in AE patients is altered only in positive APT reactions, in contrast to positive patch test reactions to contact allergens. As a consequence of this aeroallergen-induced altered epidermal barrier function, further allergens can more easily penetrate the skin, inducing a vicious circle and perpetuating the eczematous lesions.

Relationship between skin prick and atopic patch test reactivity to aeroallergens and disease severity in children with atopic dermatitis

Clinical and immunologic variables in skin of patients with atopic eczema and either positive or negative atopy patch test reactions

We evaluated the reproducibility of atopy patch test reactions and the quality and quantity of itch in 16 patients with atopic eczema and a history of a positive atopy patch test reaction, comparing three different application sites. The allergen was re-applied simultaneously on both forearms and the back. Intensity and quality of pruritus were evaluated using a visual analogue scale and the Eppendorf itch questionnaire, respectively. The atopy patch test reaction was highly reproducible, occurring in 15/16 (94%) patients. Pruritus was reported by 14/16 (88%) patients. There was no significant difference in either the intensity or quality of itch between the two forearms and the back (p>0.05). The mean peak visual analogue scale itch score was comparable across all three test sites (range 28.3-31.9). Regarding quantification of test reactions, a positive reaction was more frequent on the back (94% versus 69% on the arms) and the peak atopy patch test score was higher on the back compared with the arms (right forearm, p=0.0018 and left forearm, p=0.0683). Allergens should preferably be applied on the back for the atopy patch test. However, the atopy patch test can induce atopic itch irrespective of the application site.

Atopy patch test with different vehicles and allergen concentrations: An approach to standardization

Immunophenotyping of the cutaneous cellular infiltrate after atopy patch testing in cats with atopic dermatitis.

T Cell Epitope-Specific Defects in the Immune Response to Cat Allergen in Patients with Atopic Dermatitis

Background: Atopic eczema is a chronic inflammatory skin disease in which several subgroups of cases can be identified. Atopy patch testing (APT) reveals allergen sensitization also in atopic eczema patients devoid of detectable allergen-specific IgE, suggesting the importance of factors other than IgE in the reaction. Here we investigate the relationship between APT reactions and allergen-specific peripheral IgE and T cell reactivity in atopic eczema patients. Methods: Adult patients with atopic eczema (n = 64) and healthy controls (n = 24) were analyzed for reactivity to Malassezia sympodialis extract by APT, measurement of specific plasma IgE and in vitro determination of the frequency of allergen-reactive peripheral blood mononuclear cells producing interleukin-4 and interleukin-5 using the ELISpot method. Results: When combining the results of the APT, IgE measurements and the ELISpot analyses, reactivity to M. sympodialis was found in a majority of the atopic eczema patients (69%), whereas the healthy controls were negative throughout. T cell reactivity to M. sympodialis, manifested by production of both interleukins 4 and 5, was highly predictive for a positive APT reaction and displayed a strongly positive correlation with the APT score. In contrast, the allergen-specific IgE levels did not predict the APT outcome, and no correlation could be found between the IgE levels and the APT score. Conclusion: Peripheral allergen-specific T helper 2 cell-mediated reactivity appears to be required for a positive APT reaction to M. sympodialis. The diagnostic potential of measuring peripheral allergen-specific T cell responses should be considered in atopic eczema.