Positive Atopy Patch Test Reactions Research Articles

Atopy patch testing and associations with atopic conditions and specific IgE tests: a population-based study in adolescents

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.

Atopy patch test with house dust mite in Chinese patients with atopic dermatitis.

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.

Patch Testing for Noncontact Dermatitis: The Atopy Patch Test for Food and Inhalants

The atopy patch test (APT) is defined as a patch test procedure to assess delayed type hypersensitivity reactions against those protein allergens known to elicit IgE-mediated type I reactions in atopic patients. This patch test procedure uses intact protein allergens instead of haptens in an optimized test setting and with a special reading key. It may be clinically useful especially for atopic dermatitis, as the currently available test procedures either target the wrong reaction type (type I and not type IV) or use the wrong allergens (haptens and not protein allergen). A positive APT reaction correlates with a positive lymphocyte transformation test and allergen-specific Th2 cells in the peripheral blood. As even small changes in the test procedure influence the sensitivity, specificity, and reproducibility of the APT, the European Task Force on Atopic Dermatitis (ETFAD) has developed a standardized APT technique: Intact protein allergens, purified in petrolatum, are applied in 12-mm-diameter Finn chambers mounted on Scanpor tape for 48 h to non-irritated, non-abraded, or tape-stripped skin of the upper back for 48 h; the evaluation of the test reaction is done after 48 and 72 h using the ETFAD reading key, assessing erythema as well as number and distribution pattern of the papules. The APT may reveal type IV sensitization in patients who are negative for the respective type I tests. Limited availability of the expensive test substances and limited reimbursement is among the factors restricting the routine use of the APT.

The Expression of BAFF, APRIL and TWEAK Is Altered in Eczema Skin but Not in the Circulation of Atopic and Seborrheic Eczema Patients

The TNF family cytokines BAFF (B-cell activating factor of the TNF family) and APRIL (a proliferation-inducing ligand) are crucial survival factors for B-cell development and activation. B-cell directed treatments have been shown to improve atopic eczema (AE), suggesting the involvement of these cytokines in the pathogenesis of AE. We therefore analyzed the expression of these TNF cytokines in AE, seborrheic eczema (SE) and healthy controls (HC). The serum/plasma concentration of BAFF, APRIL and a close TNF member TWEAK (TNF-like weak inducer of apoptosis) was measured by ELISA. The expression of these cytokines and their receptors in skin was analyzed by quantitative RT-PCR and immunofluorescence. Unlike other inflammatory diseases including autoimmune diseases and asthma, the circulating levels of BAFF, APRIL and TWEAK were not elevated in AE or SE patients compared with HCs and did not correlate with the disease severity or systemic IgE levels in AE patients. Interestingly, we found that the expression of these cytokines and their receptors was altered in positive atopy patch test reactions in AE patients (APT-AE) and in lesional skin of AE and SE patients. The expression of APRIL was decreased and the expression of BAFF was increased in eczema skin of AE and SE, which could contribute to a reduced negative regulatory input on B-cells. This was found to be more pronounced in APT-AE, the initiating acute stage of AE, which may result in dysregulation of over-activated B-cells. Furthermore, the expression levels of TWEAK and its receptor positively correlated to each other in SE lesions, but inversely correlated in AE lesions. These results shed light on potential pathogenic roles of these TNF factors in AE and SE, and pinpoint a potential of tailored treatments towards these factors in AE and SE.

Epidemiology of Atopy Patch Tests With Food and Inhalant Allergens in an Unselected Population of Children

Ronchetti R, Jesenak M, Trubacova D, Pohanka V, Villa MP. Pediatr Allergy Immunol. 2008;19(7):599–604PURPOSE OF THE STUDY. The atopy patch test (APT) has been used as a diagnostic tool for patients with suspected food or inhalant allergy. The authors of this study assessed the prevalence of positive APT results with food or inhalant allergens in an unselected population of schoolchildren. The authors also evaluated the link between positive APT reactions and skin-prick tests (SPTs) for food and inhalant allergens, circulating eosinophils, and histamine skin reactivity.STUDY POPULATION. The study included an unselected population of 380 children 9 or 13 years of age living in Rome, Italy.METHODS. APTs were carried out with food (native or standardized) and inhalant allergens. All children also underwent SPTs with 5 common inhalant and 4 food allergens.RESULTS. The prevalence of positive APT reactions for foods in unselected children ranged between 4% and 11% for hen's egg, tomato, and wheat flour and was similar for the 2 age groups studied. The prevalence of positive APT reactions for milk was significantly lower in children of age 13 than in children of age 9 (P = .013). No concordance emerged between positive APT and SPT results for foods. Conversely, APT and SPT results for inhalant allergens yielded statistically significant concordance (P < .001).CONCLUSIONS. The APT produces positive reactions for food or inhalant allergens in a significant number of subjects in the general population of schoolchildren. Inhalant allergens probably induce a positive APT reaction through an immunoglobulin E–linked process, whereas food allergens probably do not.REVIEWER COMMENTS. The APT has been investigated as a new diagnostic tool for patients with food or inhalant allergies when non–immunoglobulin E–mediated reactions are considered, such as in identifying triggers for atopic dermatitis, allergic eosinophilic esophagitis, and food protein-induced enterocolitis syndrome. However, studies have demonstrated conflicting results for the utility of this test. Here, the authors investigated the prevalence of positive results of APT in an unselected population of schoolchildren and found that APTs produced positive reactions for foods in 4% to 11% of cases and for inhalant allergens in 4% to 30%, depending on the allergen used. This is important information to consider when investigating the APT as a potential diagnostic tool.

Patch test in the diagnosis of food allergy

Double-blind, placebo-controlled food challenges (DBPCFC) are the gold standard method for diagnosing food allergies. However, due to the difficulty of their performance on routine clinic, there is a need for laboratory tools in order to minimise the frequency of DBPCFC. Atopy patch test (APT) represents a promising manner of diagnosing delayed-type allergic reactions. The APT may identify patients with food allergies with negative specific IgE. However, the clinical relevance of positive APT reactions is still to be proven by standardised outcome definitions.

Elevated Peripheral Allergen-Specific T Cell Response Is Crucial for a Positive Atopy Patch Test Reaction

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.

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

Atopy patch test (APT) has been used as a diagnostic tool in patients with suspected food or inhalant allergy. This study assessed the prevalence of positive APT with food or inhalant allergens in an unselected population of schoolchildren. We also evaluated the link between positive APT reactions and skin-prick tests (SPT) for food and inhalant allergens, circulating eosinophils and histamine skin reactivity. We studied an unselected population of 380 children aged 9 or 13 yr living in Rome, Italy. APTs were carried out with food (native or standardized) and inhalant allergens. All the children also underwent skin-prick testing with five common inhalant and four food allergens. We also measured eosinophil cell counts and histamine skin reactivity. The prevalence of positive APT reactions for foods in unselected children ranged between 4% and 11% for hen's egg, tomato, and wheat flour and was similar for both age groups studied. The prevalence of positive APT for milk was significantly lower in children aged 13 than in children aged 9 (p = 0.013). No concordance emerged between positive APT and SPT for foods. Conversely, APT and SPT for inhalant allergens yielded statistically significant concordance (p < 0.001). APT produces positive reactions for food or inhalant allergens in a significant number of subjects in the general population of schoolchildren. Age influences the prevalence of positive APTs with cow's milk to some extent. Inhalant allergens probably induce a positive APT reaction through an immunoglobulin E-linked process, while food allergens probably do not.

Laser-Assisted Penetration of Allergens for Patch Testing

Patch-test patients often complain of itching and inconvenience. To demonstrate (1) the usefulness of laser-assisted alteration of the stratum corneum to enhance allergen delivery and (2) patient satisfaction with this procedure. The LAD-01 (erbium:yttrium-aluminum-garnet) laser unit was used to alter stratum corneum from patients with known sensitivity to nickel or Kathon CG. These allergens were then applied to the laser-pretreated sites for 60 minutes. Results were observed at 24, 48, and 96 hours and at 1 week. One patient who refused conventional patch testing was tested with an entire modified North American standard series tray with the laser patch-test technique. An additional patient with previously demonstrated positive atopy patch-test reactions to environmental organisms was retested with laser pretreatment to the same antigens. Three of three patients known to be sensitive to Kathon CG and eight of eleven known nickel-sensitive patients had positive reactions at the laser-pretreated sites. The patient who was tested with the entire standard series demonstrated relevant positive reactions to formaldehyde and to a textile resin. One subject with known reactions to three environmental organisms reproduced patch-test responses with laser pretreatment. No irritant reactions were noted. Patients reported no pain. With further modification, laser pretreatment may improve patient convenience and decrease irritant test reactions owing to occlusion.

Atopie-Patch-Test mit Aeroallergenen und Nahrungsmitteln

The atopy patch test (APT), a patch test employing allergens known to elicit IgE-mediated reactions which is assessed by evaluating eczematous skin lesions after 24 h to 72 h, was developed as a diagnostic tool for characterizing patients with aeroallergen-triggered atopic eczema (AE, atopic dermatitis). Positive APT reactions are associated with allergen-specific T-cell responses. The specificity of APT is higher than the specificity of skin prick tests or RAST. More studies for the standardization of APT methods are necessary, especially with regard to food APT.

Atopy Patch Test – Reproducibility and Elicitation of Itch in Different Application Sites

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.

The prevalence of positive reactions in the atopy patch test with aeroallergens and food allergens in subjects with atopic eczema: a European multicenter study

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.

High Prevalence of Cutaneous Human Papillomavirus DNA on the Top of Skin Tumors but not in “Stripped” Biopsies from the Same Tumors

Genomes of human papillomaviruses (HPV) are common in biopsies from non-melanoma skin cancers but are also found on healthy skin and it is possible that HPV positivity in tumor biopsies by PCR may merely reflect contamination of the lesion surface. To investigate this issue, 229 immunocompetent patients were tested for HPV DNA in swab samples collected on top of skin tumors and in biopsies of the same tumors, obtained after stripping with tape to remove superficial layers. HPV DNA was detected on top of 69% (159 of 229) of the lesions, and in 12% (28 of 229) of the stripped biopsies (p<0.001). The difference was seen for all four types of tumors studied. Seborrheic keratosis had 79% (34 of 43) HPV positivity on top of lesions versus 19% (eight of 43) in biopsies; actinic keratosis had 83% (38 of 46) HPV positivity on top versus 11% (five of 46) in biopsies; basal cell carcinoma had 63% (69 of 109) on top versus 8% (nine of 109) in biopsies and squamous cell carcinoma had 58% (18 of 31) on top versus 19% (six of 31) in biopsies. HPV DNA is common in superficial layers of lesions, but is not necessarily present throughout tumors.

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

Cats with spontaneously occurring atopic dermatitis have clinical and immunocytochemical characteristics compatible with these in humans with atopic dermatitis (AD). The atopy patch test (APT) has proven to be a valuable tool in elucidating the disease process in humans. Additionally, the APT is very specific and bypasses the problem of conflicting results due to differences in chronicity of lesions of AD patients. We adapted the APT for use in cats to explore the suitability of the APT as a tool to study the onset of allergic inflammation in cats with atopic dermatitis. APT were performed in AD cats (n = 6) and healthy cats (n = 10). All cats were patch tested with two allergens in three different dilutions and a diluent control. The allergens for the APT were selected from positive intradermal test and /or prick test results and consisted of: Dermatophagoides farinae, D. pteronyssinus, Tyrophagus putrescentiae, and a grass pollen mixture. APT were read after 10, 24 and 48 h, and punch biopsies for immunohistochemical evaluation were collected at these time points. Macroscopically positive APT reactions were observed in three out of six cats at 24 and/or 48 h with allergen concentrations of 25,000 and 100,000 NU/ml. Reactions were not observed at negative control sites and neither in control animals. A significantly increased number of IL-4+, CD4+, CD3+, MHC class II+ and CD1a+ cells was found in one AD cat with positive APT reactions. Five out of six AD cats had significantly increased IL-4+ T cell numbers at 24 and/or 48 h. Our data indicate that in cats, macroscopically positive patch test reactions can be induced, which have a cellular infiltrate similar to that in lesional skin. We found a high specificity and a macroscopically positive APT reaction in half of the cats, which is similar to what is seen in humans. Hence, the APT in cats might be a useful tool in studying the immunopathogenesis of feline atopic dermatitis.

Atopy patch test reactions to Malassezia allergens differentiate subgroups of atopic dermatitis patients.

The yeast Malassezia is considered to be one of the factors that can contribute to atopic dermatitis (AD). To investigate the reactivity to Malassezia allergens, measured as specific serum IgE, positive skin prick test and positive atopy patch test (APT), in adult patients with AD. In total, 132 adult patients with AD, 14 with seborrhoeic dermatitis (SD) and 33 healthy controls were investigated for their reactions to M. sympodialis extract and three recombinant Malassezia allergens (rMal s 1, rMal s 5 and rMal s 6). Sixty-seven per cent of the AD patients, but only one of the SD patients and none of the healthy controls, showed a positive reaction to at least one of the Malassezia allergens (extract and/or recombinant allergens) in at least one of the tests. The levels of M. sympodialis-specific IgE in serum correlated with the total serum IgE levels. Elevated serum levels of M. sympodialis-specific IgE were found in 55% and positive APT reactions in 41% of the AD patients with head and neck dermatitis. A relatively high proportion of patients without head and neck dermatitis and patients with low total serum IgE levels had a positive APT for M. sympodialis, despite lower proportions of individuals with M. sympodialis-specific IgE among these groups of patients. These results support that Malassezia can play a role in eliciting and maintaining eczema in patients with AD. The addition of an APT to the test battery used in this study reveals a previously overlooked impact of Malassezia hypersensitivity in certain subgroups of AD patients.

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

The yeast Malassezia furfur belongs to the normal cutaneous flora, but is also a triggering allergen that can contribute to atopic dermatitis. To illuminate the effect of circulating allergen-specific T cells in atopic dermatitis, the peripheral mononuclear cell response was correlated with the in vivo skin prick test and atopy patch test reactivity to M. furfur. None of 16 healthy controls showed any positive in vivo reaction. The 40 atopic dermatitis patients, of whom 18 had serum IgE reactivity to M. furfur, were subdivided according to their in vivo reaction to M. furfur extract into three groups: skin prick test positive/atopy patch test positive (n = 12), skin prick test positive/atopy patch test negative (n = 12), and skin prick test negative/atopy patch test negative (n = 16). The skin prick test positive/atopy patch test positive and the skin prick test positive/atopy patch test negative groups had a significantly higher peripheral mononuclear cell stimulation index than the healthy controls. Interestingly, the stimulation index values in the skin prick test positive/atopy patch test positive group were significantly higher than in the skin prick test positive/atopy patch test negative group. In the M. furfur skin prick test positive atopic dermatitis patients (n = 24) a correlation was found between stimulation index and the M. furfur atopy patch test reactions, but not between stimulation index and M. furfur-specific serum IgE levels. Skin prick test positive and/or atopy patch test positive reactions to the recombinant M. furfur allergens rMal f 1, rMal f 5, and rMal f 6 were observed in 7, 14, and 16 of the 40 atopic dermatitis patients, respectively. Further, there was a correlation between production of the T helper 2-related cytokines interleukins 4, 5, and 13 and stimulation index to M. furfur extract, but not between the T helper 1-related interferon-gamma and stimulation index to M. furfur extract. Our data strongly suggest a relationship between circulating specific T cells with a T helper 2-like cytokine profile and positive atopy patch test reactions.

Triggerung der atopischen Dermatitis durch Sporen des Austernpilzes Pleurotus pulmonarius

- Spores of the basidiomycete Pleurotus pulmonarius a species of the oyster mushrooms are widespread components in the air and established as causes of respiratory allergies. Recent reports indicate that aeroallergens such as mite allergens, pollen or animal dander may play an important role triggering atopic eczema in a subgroup of subjects with atopic dermatitis. The aim of the study was to investigate whether spores of P. pulmonarius may elicit delayed-type skin reactions in atopic subjects particularly in those with an atopic dermatitis. Sixty-five study subjects were categorized prospectively in 4 groups having atopic dermatitis or respiratory allergy with regard to the skin prick test reactivity to P. pulmonarius spore extract. Twenty nonatopic individuals served as control subjects. Atopy patch test performed with P. pulmonarius spore extract at a concentration of 1.35 mg protein per gram of petrolatum were evaluated after 48 and 72 hours. Of the subjects with atopic dermatitis, 12 of 37 (32%) showed a positive atopy patch test reaction with 7/13 (54%) also having a positive skin prick test response to the P. pulmonarius spore extract. In the study group with respiratory allergy and positive skin prick test to the Pleurotus extract 1 subject with a well-known asthma had a positive atopy patch test. No positive test reaction was observed in the nonatopic control subjects or in subjects with respiratory allergy but negative skin prick test responses to the P. pulmonarius spore extract. Our results demonstrate that spores of the oyster mushroom P. pulmonarius can induce delayed-type reactions consistent with an acute eczema in atopic individuals, particularly in those with atopic dermatitis. Furthermore, it could be shown that individuals with an air-exposed pattern of the atopic dermatitis were most reactive to the atopy patch tests with these spore extract.

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

Background: Epicutaneous application of aeroallergens induces a positive atopy patch test (APT) response in about 50% of patients with atopic eczema (AE) and sensitization for these allergens. Objective: To elucidate the mechanisms determining the outcome of the APT, the following questions were addressed. Are there differences in clinical features between patients with AE who have positive versus negative APT responses? Is a macroscopically negative APT response also histologically negative, and if so, are there differences in clinically noninvolved skin between the two groups regarding (1) the sensitivity toward an irritant, (2) the composition of cellular infiltrate, (3) the presence of aeroallergen-specific T cells, and (4) the number of IgE+ cells? Methods: Punch biopsy specimens from both house dust mite patch tested and the clinically noninvolved skin of patients with AE who have positive APT responses (n = 10) and negative APT responses (n = 10) and those from the normal skin of atopic individuals without AE (n = 10) and nonatopic volunteers (n = 10) were analyzed by using immunohistochemistry with mAbs against eosinophil cationic protein, IgE, the high-affinity receptor for IgE, and CD3 and CD25 mAbs. Furthermore, T-cell lines were propagated from noninvolved skin of all patient and control groups. The T-cell lines were tested for house dust mite specificity. Results: Negative APT sites were immunohistochemically similar to clinically noninvolved AE skin. There were no significant differences between patients with AE who had positive and negative APT results regarding either clinical features, the composition of cellular infiltrate, or the presence of allergen-specific T cells in clinically noninvolved skin. However, differences were observed regarding the presence of IgE on epidermal CD1a+ cells. Conclusion: Our results indicate that a positive APT reaction requires the presence of epidermal IgE+ CD1a+ cells in clinically noninvolved skin, but that also other, as yet unknown, discriminatory factors are involved. (J Allergy Clin Immunol 2000;105:1008-16.)

Atopy patch testing--a diagnostic tool?

Atopy patch testing--a diagnostic tool?

The 'atopy patch test' in evaluating the role of aeroallergens in atopic eczema.

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.