The role of atopy patch tests in the diagnosis of allergy in atopic dermatitis

PURPOSE OF REVIEW

Recent literature on the atopy patch test, published since 2004, is reviewed to evaluate whether the pathomechanism of the test has become more evident and whether previous studies require standardization.

RECENT FINDINGS

There is evidence accumulating that a smaller subset of patients with atopic dermatitis show only atopy patch test positivity while specific IgE to the same allergen remains negative. It is possible that local IgE-mediated reactions occur in the skin. New data bring us a step forward in understanding the role of the atopy patch test in diagnosis of allergy in atopic dermatitis but no comprehensive studies were published during the period reviewed.

SUMMARY

Despite recent advances in determining the value and indication for use of the atopy patch test in atopic dermatitis, more objective studies are needed. The atopy patch test may be useful in understanding the mechanisms of atopic allergy, and in defining the clinical relevance of the airborne allergens in eliciting dermatitis. Regarding food allergy, the atopy patch test still requires standardization. To date, methodology differs in all published papers; even the gold standard, the challenge test itself, is not appropriately standardized, which makes the interpretation of results less reliable.

Late reactions to the patch-test preparations para-phenylenediamine and epoxy resin: a prospective multicentre investigation of the German Contact Dermatitis Research Group

BACKGROUND

Late patch-test reactions, developing at day (D) 7 or later have been described for several allergens. Late reactions may reflect patch-test sensitization. Para-phenylenediamine (PPD) and epoxy resins (ER) are potent allergens and therefore may potentially induce patch-test sensitization. Up to now, there has been no prospective study on the frequency of late reactions in routine patch testing with these allergens.

OBJECTIVES

To assess the frequency of late reactions to PPD and ER.

PATIENTS/METHODS

In 1748 patients PPD (PPD-base, 1% pet.) and ER [based on diglycidylether of bisphenol A (DGEBA, 1% pet.)], and in 812 patients, nickel sulphate (5% pet.) were removed from the test panel of the standard series and applied on the medial side of the upper arm. Patch-test occlusion time was 24 h in 588 (PPD and ER) and 241 patients (nickel sulphate), respectively, and 48 h in 1160 (PPD and ER) and 571 (nickel sulphate) patients, respectively. Patch tests were read on D1-3 and D2-3, respectively; additional late readings were performed on D7, D14 and D21 after patch-test application. Patients who were not able to return for all scheduled late readings were telephoned on D7, D14 or D21, and questioned about a reaction at the test sites. Patients were instructed to perform daily self-examination from D4 onwards and to return immediately to the clinic if a reaction at the upper arm became visible.

RESULTS

Data of 1428 patients (ER and PPD) and 638 patients (nickel) were evaluable. In 25 patients (1.8%), patch tests became positive not before D7, among them 21 reactions to PPD (1.5%) and four reactions to ER (0.3%). In five of seven patients, repeated patch tests with PPD disclosed patch-test sensitization as the cause of the late reaction. All late reactions, except for one, occurred in patients in whom patch tests were applied for 48 h. No late reactions were seen with nickel sulphate.

CONCLUSIONS

PPD (1% pet.) elicited late reactions in 1.5% of routine patch tests, the majority of them probably being caused by patch-test sensitization. Therefore, the German Contact Dermatitis Research Group decided to remove PPD 1% pet. from the German standard series and to take efforts to optimize the patch-test conditions of PPD. One way to optimize PPD testing could be to reduce the exposure of PPD 1% to 24 h. Alternatively the patch-test concentration of PPD might be reduced.

A pilot study of the usefulness and safety of a ready-to-use atopy patch test (Diallertest) versus a comparator (Finn Chamber) during cow's milk allergy in children

BACKGROUND

Patch testing is used in the diagnosis of food allergy, especially during delayed manifestations.

OBJECTIVE

A ready-to-use atopy patch test (APT), the Diallertest, was compared with another APT device, the Finn Chamber, in pediatric cow's milk allergy.

METHODS

This prospective study involved 49 children (34.3 +/- 17 [mean +/- SD] months of age), with cow's milk allergy manifested by atopic dermatitis (10.2%), digestive manifestations (40.8%), or both (49%). All children underwent both APT techniques, with a reading 72 hours after application, followed by a milk elimination diet for 4 to 6 weeks and open cow's milk challenge.

RESULTS

A positive result was seen in 22 (44.8%) versus 13 (26.5%) patients with the ready-to-use and the comparator APTs, respectively. No side effects were recorded. Both techniques were concordant in 67.3% of patients. Of the total 41 open cow's milk challenges, 60.9% had positive results, with 8 patients lost to follow-up. The performances of the ready-to-use and comparator APTs were as follows: sensitivity, 76% (95% CI, 59.2% to 92.7%) versus 44% (95% CI, 24.5% to 63.4%; P = .02); specificity, 93.8% (95% CI, 81.9% to 100%) versus 93.8% (95% CI, 81.9% to 100%); positive predictive value, 95% (95% CI, 85.4% to 100%; 1 false-positive result) versus 91.7% (95% CI, 76% to 100%; 1 false-positive result); negative predictive value, 71.4% (95% CI, 52% to 90.7%; 6 false-negative results) versus 51.7% (95% CI, 33.5% to 69.8%; 14 false-negative results); and test accuracy, 82.9% (95% CI, 71.3% to 94.5%) versus 63.4% (95% CI, 48.6% to 78.1%; P = .05).

CONCLUSION

The ready-to-use APT exhibited a good sensitivity and specificity, with no side effects.

Drug patch testing in systemic cutaneous drug allergy

Patch testing with the suspected compound has been reported to be helpful in determining the cause of a cutaneous adverse drug reaction (CADR) and in studying the pathophysiological mechanisms involved. The main advantages of drug patch tests are that they can be done with no hospital surveillance because they induce only rarely adverse reactions and that any commercialized form of a drug can be used. In contrast, intradermal tests can be performed only with injectable forms or with a pure and sterile form of the drug. It is advised to perform drug patch tests during the 6 months following the CADR as we do not know whether positive results will persist. Due to the possibility that a low concentration might yield false negative results, drug patch tests have to be performed with rather high concentrations of the commercialized form of the drug, mostly diluted at 30% in petrolatum and/or in water. For some drugs and severe CADR, it is necessary to tests with lower concentrations or in other vehicles. Drug patch tests are positive in ca. 32-50% of patients who have developed a CADR. The clinical relevance of drug patch tests depends on the clinical features of the CADR (valuable in testing generalized eczema, systemic contact dermatitis, maculopapular rash, acute generalized exanthematous pustulosis, fixed drug eruption) and on the involved drug. As false positive results can be observed, it is always necessary to consider the relevance of any positive drug patch test. Their specificity and their negative predictive value have not been yet determined.

Patch-test-induced subjective complaints

BACKGROUND

Many patients report subjective complaints during epicutaneous patch testing.

OBJECTIVE

To demonstrate the possible relationship between the occurrence of subjective complaints and patch testing.

METHODS

All consecutive patients who were referred to our clinic for patch testing, during 1 year, were investigated to study a possible association of the patch test procedure and subjective complaints like tiredness, shakiness or feeling unwell. The patients were asked to fill in a form concerning subjective complaints on the days of the investigation. Only those without complaints on the day the patches were applied were included in the study (n=102).

RESULTS

Of the 102 patients, 17 had complaints on both days 2 and 3, 14 only on day 2, 6 only on day 3 and 65 did not develop any complaints at all. The number of patients with complaints on both days 2 and 3 (n=17) was larger than was to be expected from chance (n=4.6; p<0.01). There was a significant correlation between the number of positive patch test reactions and the number of complaints on day 2 (r=0.19; p<<0.001) and on day 3 (r=0.15; p<0.001). Positive patch tests were found in 72.2% of the patients who reported the complaint of shakiness; this proportion is significantly higher than expected from chance (p<0.05).

CONCLUSION

The results confirm those of our earlier study and demonstrate that patch testing can cause subjective complaints, especially when positive patch tests are present.

A systemic reaction to patch testing for the evaluation of acute generalized exanthematous pustulosis

BACKGROUND

Patch tests are considered safe but adverse reactions have been reported.

OBSERVATIONS

A case of acute generalized exanthematous pustulosis (AGEP) provoked by a patch test with acetaminophen is described. Of special interest are the negative patch test results obtained with the offending drug. The case is discussed against the background of the putative mechanisms of AGEP and the reported systemic reactions to patch testing for AGEP.

CONCLUSIONS

To our knowledge, this is the first report in the English-language literature of a generalized AGEP-like reaction caused by patch tests carried out to determine the drug eliciting AGEP.

Erythema multiforme due to contact with weeds: a recurrence after patch testing

Erythema multiforme (EM) as a complication of patch testing (PT) is rare. A 52-year-old woman with a 13-year history of episodes of EM, after contact with weeds during home gardening, had had no recent history of herpes simplex, other infection, drug ingestion or vaccination. On examination, EM lesions were distributed on the exposed skin. 5 weeks after complete resolution, PT and photopatch testing (PPT) were done with fresh plants she brought in. She was PT with a standard series and the Hermal-Trolab plants, woods, tars, balsams and flavors series. Intradermal testing, with a 3 + reaction to mixed weed pollens, was done 3 weeks later. Specific IgE to weed pollens class 1 (CAP-Pharmacia) was detected. Eczematous PT reactions were obtained with fresh leaves: common chickweed (Stellaria media Caryophyllaceae), dandelion (Taraxacum officinale Compositae), field-milk thistle (Sonchus arvensis Compositae) and white clover (Trifolium repens Leguminosae). Photoaggravation was seen to common chickweed and dandelion. Positive PT was also seen with alantolactone. By the 4-day reading, a typical EM had commenced, coming up to quite the same extent as seen on admission. There was no photosensitivity (UV skin tester, K. Waldmann). In the essential oil obtained from common chickweed, thin layer chromatography (TLC) revealed the well-known contact allergens borneol, menthol, linalool, 1,8-cineole, and other terpenes such as epoxy-dehydro-caryophyllene, monoterpene alcohol-ester and caryophyllene. Up to now, no data on essential oil in Stellaria media (common chickweed) have been reported. It can be concluded that EM developed due to contact with weeds, and recurred after patch testing. Neither blistering nor eczematous lesions have been seen on her skin, making this case very unusual. As far as the world literature is concerned, this is only the 4th report of EM developing in association with patch testing.

Necrotizing cellulitis caused by Apophysomyces elegans at a patch test site

Plant material occasionally is used in patch testing to diagnose contact dermatitis. Serious adverse reactions to this practice are extremely uncommon. The authors report on a 68-year-old non-insulin-dependent diabetic gentleman with hand dermatitis in whom severe necrotizing cellulitis developed caused by Apophysomyces elegans, a subtype of mucormycosis, at the site of a patch test to a snapdragon plant from his garden.

Epicutaneous patch testing

Epicutaneous patch testing is still regarded as the best method of diagnosing allergic contact dermatitis. The present patch test technique is the result of a continuous process of development and improvement since its first application in the late 19th century. During the last decades of the 20th century a lot of effort was put into standardization of materials and methods used in patch testing. Patch tests can be used to confirm a suspected allergic contact dermatitis and either to recommend avoidance of particular products or to recommend alternative products in a particular patient. The true rate of clinically relevant hypersensitivity in positive patch test reactions remains to a great extent unknown. The ideal patch test should cause as few adverse reactions as possible, but a lot of adverse reactions have been described. How-ever, it has to be noted that the overall risk-benefit equation of patch testing is in favor of the benefit, if performed correctly and with the proper indications. A careful history taking and attention to the clinical picture are key actions to facilitate the interpretation of the clinical relevance of the epicutaneous patch test results.

Locally invasive cutaneous Apophysomyces elegans infection acquired from snapdragon patch test

Apophysomyces elegans is an environmental fungus related to other well-known agents of zygomycosis. We report a case of locally invasive A elegans soft tissue infection resulting from the application of a skin patch to test for snapdragon sensitivity. The infection was limited to skin and soft tissue, and treatment consisted of local debridement and liposomal amphotericin B. Outcome was successful.

Excited skin syndrome: study of 39 patients

BACKGROUND

Excited skin syndrome (ESS) is an adverse reaction obtained when carrying out epicutaneous patch tests, characterized by multiple positive test results, associated with one or more strongly positive tests, which are not all reproduced when the patient is tested afterward.

OBJECTIVE

The aim of this study was (1) to determine the frequency of ESS in patients submitted to patch testing, (2) to confirm the influence of the evolution time of the primary dermatosis with ESS induction, (3) to determine differences among patients according the rate of positive test loss, and (4) to compare the number of positive tests for each substance between the first test, when all allergens in the test battery were applied, and the second test, when only the allergens with positive tests on the first occasion were applied at a greater distance from one another.

METHODS

Epicutaneous tests were carried out in 630 patients with a suspected diagnosis of allergic contact dermatitis. Patients presenting 2 or more positive test results were considered to have ESS and were submitted to a second patch test.

RESULTS AND CONCLUSIONS

ESS developed in 39 of the 630 patients tested, corresponding to a frequency of 6.2%. Analysis of data found a longer duration of the primary dermatitis in patients who in whom ESS developed compared with those who did not. Parabens, fragrance mix, and thimerosal had more positive patch test reactions using standard application techniques relative to the retest procedure, which placed the substances at a greater distance from one another, suggesting that, in addition to the factors previously reported to influence the reduction of ESS, the position of the allergens in the testing procedure also should be considered.

The risk of active sensitization to PPD

Para-phenylenediamine (PPD) and para-aminoazobenzene are strong sensitizers. By the patch test procedure, the patient may be sensitized to these agents. Combined testing of para-compounds may increase the risk of active sensitization. We studied the % of positive patch test reactions and their relevance. In order to assess the risk of active sensitization, we compared the % of relevant reactions of both early (2/3 days) and late (7 days) reactions. We also compared the percentage of positive patch test reactions to PPD and their relevance if simultaneously tested with para-aminoazobenzene. We studied the patch test reactions to PPD in the routine series in 2058 patients. In a group of 678 patients we tested PPD and para-aminoazobenzene simultaneously. 4.3% and 3.1% of the patients reacted to PPD, respectively, with and without simultaneous testing with para-aminoazobenzene. We estimated the reactions as relevant in 21.1% and 39.7%, respectively, with and without simultaneous testing with para-aminoazobenzene. We considered none of the late reactions as relevant. We found a high proportion of relevant patch test reactions to PPD, but sensitization to PPD by the patch test procedure is a risk. We state that routine series should not contain PPD. The high number of irrelevant late positive reactions strongly suggests active sensitization. Moreover, PPD is not a ubiquitous allergen and can be tested on a non-routine basis if industrial exposure to para-compounds is suspected or if a specific localization (e.g., head or feet) prompts the testing of PPD. Testing PPD combined with para-aminoazobenzene does lead to a slight increase in positive reactions to PPD (p<0.25) and to an increase in irrelevant reactions (p<0.10).

(Un)usual effects of patch testing?

BACKGROUND

Little information is available concerning subjective complaints associated with patch testing.

OBJECTIVES

To gather information about the frequency and the nature of such complaints, and to evaluate, if possible, whether the complaints were really caused by patch testing.

PATIENTS/METHODS

Four hundred and thirty-three patients took part in a questionnaire study between December 1996 and October 1997. Complaints of itch and other subjective complaints, such as tiredness and feeling unwell, were recorded.

RESULTS

From the total group of 433 patients, 379 patients (87%) recorded one or more complaints on day 0. By day 2 this number was 383 patients (88%), with a significant reduction to 326 patients (75%) by days 3-4. Most complaints concerned itch on the back, and to a lesser extent tiredness. Fifty-four patients (54 of 433; 12%) did not report itch or other subjective complaints on day 0; of this group, 36 patients (66%) developed complaints by day 2. By days 3-4, 24 patients (44%) reported complaints: 20 patients from the day 2 group (37%) and four patients (7%) from days 3-4. Again the largest increase in complaints was found for itch on the back, but other complaints were also found to have increased, mainly tiredness, feeling unwell, headache, shakiness and light-headedness.

CONCLUSIONS

We conclude that patch testing can, in addition to local skin reaction and itch, also cause other subjective complaints in a number of patients.

Pitfalls in patch testing

Patch testing is an invaluable diagnostic tool in the evaluation of allergic contact dermatitis. While TrueTest has simplified the technique for many practitioners, there remains potential for error. We asked 4 experts to describe their approach to several dilemmas encountered in patch testing. Their responses will be helpful to both the veteran and tyro.

Symptoms and signs reported during patch testing

BACKGROUND

In a pilot questionnaire study, there was a high frequency of subjective complaints and distant skin reactions during patch testing as reported at the day of test reading, particularly in female patients.

OBJECTIVE

To document in a controlled study possible side-effects of a generalized nature occurring during the test procedure.

METHODS

A questionnaire study on symptoms and signs reported at application and at reading of standard patch tests was conducted with 401 patients, with the patients serving as their own controls.

RESULTS

An eczematous flare-up during patch testing was observed in 3.7% of the patients. There were plenty of different symptoms of malaise but, with one exception (itch on the back), the number of symptoms tended to be less on the day of reading than on the day of application of the tests. This held true also for itch occurring in the patients' dermatitis. There was no statistical correlation between symptoms and signs on the one hand and positive patch tests on the other.

CONCLUSION

Distant skin reactions and impairment of general health occurring during patch testing are often reported at the time of test reading. However, with the exception of itch on the back, symptoms and signs are rather less common after the application of patch tests than before.

Thoughts on sensitizers in a standard patch test series. The European Society of Contact Dermatitis

Patch testing is the predominant method of establishing contact allergy. The present patch test technique is the result of a continuous process of development and improvement since its first application in the late 19th century. The perfect patch test should give no false-positive and no false-negative reactions. The ideal patch test should also cause as few adverse reactions as possible, particularly no patch test sensitization. Even though the history and examination of a patient with suspected allergic contact dermatitis will give clues to possible sensitizers, it is not sufficient to patch test only with initially suspected sensitizers; unsuspected sensitizers used for patch testing frequently turn out to be the real cause of the dermatitis. Fortunately, a small number of substances are considered to account for the majority of delayed hypersensitivity reactions. Therefore, generally 20-25 test preparations consisting of chemically defined compounds, mixes of allergens, and natural and synthetic compounds, are grouped into a standard test series. The requirements to be fulfilled by a sensitizer in a standard patch test series are discussed in this article. A procedure of investigations is proposed before a sensitizer is included in a standard series.