The American Academy of Dermatology patch test series for contact dermatitis

Brazilian experience with atopy patch tests for Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis

Background

The aim of this study was to evaluate the positivity rates of atopy patch tests for Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis in patients with respiratory diseases such as asthma and allergic rhinitis with or without atopic dermatitis.

Methods

The patients’ clinical histories were collected, and the patients were subjected to skin prick and patch tests with the three different house dust mites on the same day. The patch tests were examined 48 hours later, and then patients were divided into two groups: I- patients with respiratory diseases, such as asthma and/or rhinitis, and atopic dermatitis and II-patients with only respiratory diseases. A total of 74 patients ranging in age from 2 to 60 years were included in this study; 16 patients were included in group I and 58 were included in group II. This study was approved by the human ethics committee of the Faculty of Medical Science and Health SUPREMA (number 2.007.135), and written informed consent was collected from each patient or their parents prior to enrollment.

Results

In the skin prick tests, the most prevalent mite that evoked a reaction was Dermatophagoides pteronyssinus, followed by Dermatophagoides farinae and Blomia tropicalis. Regarding the atopy patch tests, the mite that most frequently induced a positive reaction was Dermatophagoides farinae (78.4%), followed by Dermatophagoides pteronyssinus (77%) and Blomia tropicalis (52.7%). A comparison of the skin prick and atopy patch tests revealed that 53 patients (71.6%) were positive on both tests, and 30 (56.6%) patients were positivite for the same mite. We found six patients (8%) who had a positive clinical history of allergy and only exhibited positivity on the atopy patch test.

Discussion

Most studies have been performed with atopic dermatitis patients, but in this study, most of the patients had respiratory conditions. Blomia tropicalis is a mite that is prevalent in tropical areas, such as Brazil, and only two publications include these three mites, wich are present in Brazil. The APT may produce positive results in concordance with the SPT resuts, but may also be the only positive test ( 8%) as we observed in our study. These results suggest that the mite atopy patch test is relevant and should be considered as an additional test for patients with clinical histories of allergic respiratory disease who have negative prick test results.

Conclusion

The APT should be considered as an additional test when the SPT and specific serum IgE tests are negative in patients with clinical histories of allergies.

Prevalence of positive atopy patch test in an unselected pediatric population

Background

In the latest decades, epidemiological studies on allergic disorders in children, including atopic dermatitis, rhinitis and asthma, demonstrated a continuous increase in prevalence. However, such studies are usually performed by questionnaires and, sometimes, by skin prick test or in vitro IgE tests, while the portion of allergy sustained by the cell-mediated mechanism is neglected, because the essential test, i.e. the atopy patch test is not performed.

Methods

This cross-sectional survey studied by a specific questionnaire, skin prick test and atopy patch test, an unselected population, represented by the entire scholastic population attending a Primary school and a Junior Secondary school in the rural town of San Marco in Lamis, 12.000 inhabitants (Puglia, Italy).

Results

Among the 456 subjects included, 78 (17.1 %) had a positive skin prick test and 57 (12.5 %) had a positive atopy patch test. In particular, 13.4 % of subjects were positive only to skin prick test and 8.8 % were positive only to atopy patch test. The allergen most frequently positive was the house dust mite, with 41 positive results to skin prick test and 55 to atopy patch test, while for pollen positive results concerned almost exclusively the skin prick test.

Conclusions

This survey on an unselected population of children detected a prevalence of positive results to atopy patch test not so distant from the positive results to skin prick test, and in 8.8 % of subjects the atopy patch test was the only positive test. This would suggest to add the atopy patch test in future epidemiological studies on allergy, in order to avoid to overlook the not negligible portion of patients with T-cell-mediated allergy.

Factors associated with different results of allergy tests in children with dust mite-induced atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a public health problem, with an increasing prevalence worldwide. AD is a chronic inflammatory disease characterised by skin lesions and severe itching. Immunologically, AD has two forms, IgE-mediated and cell-mediated, but it may also be idiopathic. In the pathogenesis of AD, the gene mutations for filaggrin, a filament-aggregating protein present in the epidermis, are of pivotal importance, but other genetic factors are also operating, including those linked to family atopy.

METHODS

We evaluated the role of family atopy, and of the results of the atopy patch test (APT) in parents, in children with mite-induced AD. 64 children, 38 males and 26 females, mean age 4.97 years, were included for the diagnosis of AD and underwent APT and skin prick test (SPT) with dust mite extracts, with evaluation of atopy and result of APT also in parents.

RESULTS

A positive family history of atopy was shown for children with positivity to both APT and SPT compared to those with negative or only one positive result to APT or SPT (p=0.08). Significant associations were found concerning APT results in children and parents. In particular, children of a positive-APT parent had an 18-fold higher risk of APT-positivity in comparison with children of negative-APT parents, while the risk was 6.6-fold higher if APT was positive in father.

CONCLUSION

Family atopy and a positive APT in fathers are risk factors to develop cell-mediated AD, as assessed by the APT, in children.

House dust mite-related allergic diseases: role of skin prick test, atopy patch test, and RAST in the diagnosis of different manifestations of allergy

The atopy patch test (APT) was recently defined as an important tool in diagnosis of atopic dermatitis (AD) and also of rhinitis and asthma caused by hypersensitivity to the house dust mites. We evaluated 465 children (279 males and 186 females) aged 0.4-17.6 years (mean 6.6 +/- 3.8 years), by dividing them into four groups: group A, current AD (40 patients); group B, current AD with respiratory symptoms (156 patients); group C, past AD with respiratory symptoms (203 patients); and the control group, respiratory symptoms with no history of AD (66 patients). The APT was significantly more frequently positive in groups with current AD (groups A and B) or past AD (group C) than in the control group, while skin prick test (SPT) and radioallergosorbent test (RAST) were significantly more frequently positive in the control group. With multivariate analysis, for APT, significant differences were found in the comparison between group A vs group B (odds ratio (OR) 1.55) and between group A vs group C (OR 1.81). The mean age was significantly lower in group A than in groups B, C, and the control group and with less significance in groups C vs D. Children sensitized to mites with current or past AD, with or without respiratory symptoms, have a different response to diagnostic tests, which is characterized by a highly significantly more frequent positive APT in comparison with subjects who have respiratory symptoms but a negative history for AD, who show the common response to SPT and RAST.

Relationship between the atopy patch test and clinical expression of the disease in children with atopic eczema/dermatitis syndrome and respiratory symptoms

BACKGROUND

The atopy patch test (APT) may be the only positive skin test result in patients with either atopic eczema/ dermatitis syndrome (AEDS) or respiratory abnormalities with or without AEDS.

OBJECTIVE

To investigate the possible significance of APT to dust mite by comparing the positive result to this test with that of the skin prick test (SPT) in patients with different characteristics.

METHODS

A total of 297 individuals (178 boys and 119 girls) aged 5 to 221 months (mean [SD] age, 64.5 [42.1] months; median age, 58 months) were included in this study. Participants were divided into 4 groups: current AEDS, current AEDS and respiratory symptoms, past AEDS and respiratory symptoms, and respiratory symptoms with neither current nor past AEDS (control group). All the patients underwent SPT and APT using house dust mite extract.

RESULTS

In the study groups, the rate of positivity was significantly higher for APT, whereas in the control group, there were significantly more positive results to SPT (P < .001 for both). Multivariate analysis showed that there was a high probability of a positive APT result in patients with AEDS (odds ratio [OR], 17.4), with AEDS and respiratory disease (OR, 21.9), and with past AEDS and respiratory disease (OR, 22.8).

CONCLUSIONS

These patients with AEDS showed 2 different patterns of allergic response to allergens, one IgE mediated (as evaluated by positive SPT results) and the other cell mediated (as evaluated by positive APT results). The former seems to follow the so-called atopic march model, and the latter persists even after the disappearance of AEDS and is likely to be implicated in the pathogenesis of respiratory allergy.

Results of routine patch testing of 834 patients in Turin

834 consecutive patients (630 female), aged between 26 and 46 years, who were suspected of having allergic contact dermatitis were patch tested with the GIRDCA standard series during 1989-1990. The most frequent sensitizers observed included nickel sulphate, cobalt, Kathon CG, perfumes, potassium dichromate and balsam of Peru. We have evaluated the influence of individual factors such as sex, age and occupation on the patch test results, and the coexistence of 2 or more unrelated but statistically significant sensitivities.