Perfection of skin testing technique. A review

Investigation of the diagnostic performance of prick test with two environmental allergens in dogs with atopic dermatitis: A study using intradermal test as the gold standard

BACKGROUND

There are no studies investigating the correlation between prick test (PT) and intradermal test (IDT) with environmental allergens in dogs with atopic dermatitis (AD).

OBJECTIVES

To investigate the correlation between PT and IDT for two environmental allergens, and to calculate the sensitivity, specificity and Youden index of PT, using IDT as the gold standard.

MATERIALS AND METHODS

Twenty-two dogs with AD were selected. PT was performed with glycerinated allergen extracts, along with negative and positive controls, using the Greer Prick System. Reactions were interpreted (positive/negative) subjectively and by using seven objective criteria, by an examiner blinded to the IDT results. IDT reactions to the same allergens were interpreted, subjectively and objectively, by another masked investigator. The agreement between PT and IDT, the sensitivity, specificity and Youden index of PT, using IDT as gold standard, were calculated.

RESULTS

On subjective evaluation, the correlation between PT and IDT was poor and sensitivity of PT was 0%. Of the seven criteria for the objective evaluation of PT, the best diagnostic performance was attained when allergen-induced wheals were considered positive if their longest diameter was ≥8.5 mm. However, even then, the correlation with IDT was moderate, and the sensitivity of PT, albeit based on few positive IDT reactions, was low.

CONCLUSION AND CLINICAL RELEVANCE

At least as performed herein, PT has a poor-to-moderate correlation with IDT, mainly as a consequence of the lack of positive PT reactions. Further studies are needed to improve PT technique, yet, meanwhile, it cannot be recommended as a substitute for IDT.

Safety of yellow fever vaccine administration in confirmed egg-allergic patients

Yellow fever vaccine (YFV) is recommended in endemic areas but represents a risk for egg-allergic patients, as it is cultivated in embryonated eggs. This study aims to describe the outcomes of yellow fever vaccination in patients with confirmed egg allergy (EA). Methods:A prospective study was conducted from January 2018 to September 2019. EA was diagnosed through positive oral food challenge (OFC), recent history of anaphylaxis following egg contact (anaphylaxis in the last 6 months) or immediate allergic reaction in the last 2 months with positive specific IgE. A skinprick test (SPT) with YFV was performed. If the SPT was negative, an intradermal test (ID) was performed at a 1:100 dilution. If the ID was negative, a full dose of YFV was administered. If the skin prick test or ID were positive, the YFV was administered using a graded dosing protocol. Results: It was included 58 patients with confirmed egg allergy (36 M:22F), with a median age of 2.3 years (0.7-13.9 y/o). Forty-two patients had a positive OFC. Nine reported recent anaphylaxis. The other 7 had reactions in the last 2 months with positive specific IgE. During OFC, 15 presented anaphylaxis, while the other 27 presented hives and/or angioedema or vomiting. SPT with YFV was negative in all patients. ID was negative in 48 patients who uneventfully received a full dose of YFV. Ten patients had a positive ID and received YFV in graded doses. Six patients presented a mild reaction controlled with antihistamines, and 4 patients received the vaccine without reactions. Positive ID was significantly related to the vaccine reaction (p < 0.0001). Administration of YFV using a specific protocol was safe even in anaphylactic patients. However, we recommend performing the ID, which can help predict a higher risk of vaccine reaction. An appropriate setting is required to control adverse events.

Early detection of allergic diseases in otorhinolaryngology

Asthmatic diseases have been reported since the ancient world. Hay fever for instance, was described for the first time in the late 18(th) century, and the term "allergy" was introduced about 100 years ago. Today the incidence of allergies is rising; almost one third of the Western population suffers from its side effects. Allergies are some of the most chronic medical complaints, which results in high health expenditures. Therefore, they have a large health and political relevance.Caused by genetic and environmental factors, the group of IgE mediated allergies is large. It consists of e.g. atopic dermatitis, allergic asthma or allergic rhinitis. This paper aims to emphasize the ways of early diagnosis of allergic rhinitis (AR) as AR represents the most important representative of allergic diseases in ENT.

Skin prick tests and allergy diagnosis

Skin testing remains an essential diagnostic tool in modern allergy practice. A significant variability has been reported regarding technical procedures, interpretation of results and documentation. This review has the aim of consolidating methodological recommendations through a critical analysis on past and recent data. This will allow a better understanding on skin prick test (SPT) history; technique; (contra-) indications; interpretation of results; diagnostic pitfalls; adverse reactions; and variability factors.

Children's rating of itch: an experimental study

Little is known about children's ability to assess itch. The present paper aimed to investigate the discriminative capacity of two itch rating scales in children. Sixty healthy children, 4 to 12 years of age, participated. Itch was provoked with three histamine concentrations (0.1, 1.0, and 10 mg/ml). Physiologic saline was the negative control. The test solutions were pricked with a lancet into the skin of the lower arms in random order under coded conditions. The overall itch intensity for each skin prick was rated with a 100-mm visual analog scale and a four-stepped verbal rating scale (none, mild, moderate, and severe itch). In addition, the itch duration and flare response were recorded. A significant dose-response relationship was shown for the itch duration and itch intensity as rated with both scales. This was also true for the flare response, indicating a correct skin prick technique. However, children 4 to 5 years of age rated the itch intensity (both scales) less well than those aged 6 to 12 years. The younger age group discriminated between saline and histamine, but not between the different histamine concentrations. In conclusion, children aged 6 to 12 years were able to discriminate between different itch stimulus strengths in a dose-dependent way with a 100-mm visual analog scale and a four-stepped verbal rating scale, indicating the validity of these scales for measurement of experimental itch in children 6 years or older.

Cutaneous testing for allergy diagnosis: comparison of methods in common use

Practitioners who treat allergic patients must be familiar with the tests that are available to assist them in establishing the diagnosis. They must also understand the strengths and weaknesses of each of the techniques, devices, and grading systems at their disposal and that there is no criterion standard skin test. This article discusses the various techniques used in skin testing for allergy, their grading systems, and their advantages and disadvantages.

Assay of prick test inoculum volume. II. Average values and individual variability

INTRODUCTION

The amount of reagent introduced into the skin by a prick test is critical in studies on the reproducibility and standardization of the method.

OBJECTIVE

The purpose of the present study was to measure the average volume and the individual variability of the inoculum performed with a prick test standardized technique.

METHODS

Two hundred forty prick tests--16 inoculations per subject--were performed on the volar sides of arms of 15 healthy volunteers. The tests were performed by a skilled tester whose technical performance complied with the criteria of good reproducibility described in international guidelines. A 1-mm tip standard device and a 50% glycerosaline solution labeled with Tc99m were used for the test. The inoculum size was calculated using a direct assay method based on the gamma camera.

RESULTS

The average volume of the prick test inoculum was equal to 0.016 microliters, with a remarkable dispersion of the values around the mean (median, 15906: range, 418 to 82253 picoliters). Further, we observed great variability from one subject to another and great variability in the same subject from one skin site to another. A statistical analysis of the data shows that this variability depends on the individual characteristics of the subjects examined. A skilled tester using a standardized technique is not responsible for significant variability.

CONCLUSIONS

Even when performed by a skilled operator and with standardized techniques, the prick test shows great limits of reproducibility, at least as far as the size of the inoculum volume is concerned. The variability of the inoculum depends, in a statistically significant way, on the subject's individual characteristics and therefore can be reduced only within certain limits by the standardization and perfectibility of the technique.

The induction of a prolonged increase in microvascular permeability by human mast cell chymase

Chymase is a major constituent of the secretory granules of human mast cells, but little is known of the contribution of this serine proteinase in acute allergic reactions. We have purified chymase from human skin tissue, and have investigated its potential to induce microvascular leakage in vivo. Injection of chymase into the skin of guinea pigs provoked an increase in microvascular leakage within 20 min. Although skin reactions were smaller than those elicited with similar quantities of histamine at this time point, they were much longer-lived, and were still apparent 120 min following injection. Chymase induced microvascular leakage was reduced in the presence of soybean trypsin inhibitor, and abolished by heat inactivating the enzyme, indicating dependence on an intact catalytic site. Little evidence was found for synergistic interactions between chymase and either histamine or tryptase. Antihistamine pretreatment of animals did not reduce the magnitude of skin reactions to chymase suggesting that they were not mediated by histamine release. Chymase could contribute to increases in microvascular permeability following mast cell degranulation in allergic disease.

Allergy skin tests for inhalants and foods. Comparison of methods in common use

Many types of skin tests have evolved from Blackley's early scratch tests. This review highlights both the similarities between current skin tests and their differences. All current skin tests are capable of detecting allergic hypersensitivity, but the tests differ in their sensitivity, specificity, safety, reproducibility, and applications. Common factors in initial and final test doses, and in test dose increments, are identified. Test methods that quantitatively measure a range of allergen concentrations have diagnostic advantages in terms of safely detecting a wide range of allergic sensitivities. Failure to detect the full spectrum of allergic disease can lead to treatment failure; therefore, complete skin testing is desirable. This is especially important when dealing with exquisitely sensitive patients, such as many grass or ragweed sensitized patients, but is equally vital when evaluating low sensitivity patients, including many who are mold or food sensitive. Quantitation also improves test reproducibility, which is why it is used for antigen standardization. Finally, quantitation has advantages when used to initiate and escalate allergen immunotherapy. In vivo testing continues to evolve. New types of prick testing devices, and refinements of intradermal and patch test methods, continue to be reported. All allergists need to stay current with developments in vivo testing, so that they can offer their patients diagnosis that is appropriate to each individual situation.

The relationship between RAST and skin test results in patients with asthma or rhinitis: a quantitative study with purified major allergens

BACKGROUND

Study of the relationship between skin test results and IgE antibody levels is seriously hampered by the use of conventional allergen extracts because the precise amount of relevant allergen for each patient is unknown.

OBJECTIVE

This study was designed to investigate skin reactivity with purified major allergens and to assess the relation with serum levels of IgE antibodies and to determine which additional factors contribute to the skin test result.

METHODS

We used five purified major allergens (Der p 1, Der p 2, Fel d 1, Lol p 1, and Lol p 5) in skin tests, RASTs, and histamine release tests in 43 multisensitized patients with asthma or rhinitis.

RESULTS

The differences in biologic activity of the five major allergens at a given level of specific IgE are within one order of magnitude. A significant residual variation remains in the correlation between skin test results and levels of IgE antibodies, which cannot be explained by imprecision of both tests (Pearson log skin test vs log specific IgE: r = 0.46-0.92). With similar levels of specific IgE, the amount of allergen that is required for a positive skin test result may differ by as much as a factor of 100 between patients. The amount of total IgE in serum contributes significantly to the skin test result. High values of total IgE are accompanied by a lower skin reactivity for allergen. Within individuals, allergens that cause skin test results that deviate from the prediction based on IgE antibody level often show a similar deviation in the histamine release test. This indicates that the type of IgE response (i.e., affinity or epitope recognition pattern) contributes significantly to the skin test result. Skin reactivity for histamine does not significantly influence the skin reactions expressed as allergen threshold. However, increased skin reactions with higher allergen dosages depend on histamine reactivity.

CONCLUSION

The major allergens tested show similar biologic activities. In addition to IgE antibody level, total serum IgE and type of IgE antibody response contribute significantly to the skin test threshold for allergens. Even in a system with purified allergens, IgE antibody levels and skin test results are not interchangeable as an indicator of the degree of allergic sensitization.

Epigallocatechin gallate. The major causative agent of green tea-induced asthma

We describe three patients who worked in green tea factories and developed asthmatic and nasal symptoms after exposure to green tea dust. To clarify what component(s) of green tea leaves might be responsible for causing asthma, we prepared catechins, the major components of green tea leaves. Epigallocatechin gallate (EGCg; MW: 458 daltons), a major catechin, was purified by high-performance liquid chromatography. Subjects included three patients with green tea-induced asthma, five asthmatics with no previous exposure to tea dust, and five healthy controls. It was found that all three patients exhibited an immediate skin and bronchial response to EGCg. Prausnitz-Küstner test with EGCg was also positive. However, none of the asthmatic and healthy controls showed a positive reaction. These results indicate that EGCg is a causative agent of green tea-induced asthma and suggest that an IgE-mediated response is, at least in part, responsible for causing this type of occupational asthma.

A novel bioactivity assay for monoclonal antibodies directed against IgE

A novel bioactivity assay has been developed to quantitate the biological activity of a humanized, monoclonal anti-IgE antibody (rhuMAbE25) in human whole blood. Heparinized blood specimens from prescreened healthy donors were sensitized for 2 h with a constant amount of human plasma containing IgE specific for ragweed and then challenged with ragweed allergen. Histamine was released in a dose-dependent fashion and reached plateau levels after 30 min. As expected, the release of histamine by ragweed allergen was time, temperature and Ca2+ dependent, and could be enhanced by the presence of 33% deuterium oxide. Allergen-triggered release could be inhibited by rhuMAbE25 with an effective dose range from 0.1 to 1 microgram/ml. Preincubation with other humanized MAbs, which exhibit 95% homology to rhuMAbE25 but differ in epitope specificity, failed to inhibit the ragweed-induced histamine release. Overall, this bioactivity assay has a low interassay variability (%CV) of 17% (n = 23) and can be readily modified to determine if rhuMAbE25 or other anti-allergy therapeutics are capable of blocking histamine release elicited by other allergens. Moreover, the assay can be used to confirm IgE-mediated allergic responses and to provide early information regarding safety and potential efficacy of therapeutics aimed at blocking IgE dependent responses.

Comparison of the sensitivity and precision of four skin test devices

Twenty volunteers were skin tested with seven concentrations of histamine phosphate and a glycerosaline control to determine the relative sensitivity and precision of four skin test devices: Greer Pen (GP), Greer DermaPIK (DP), Center Multi-Test (MT), and Morrow Brown needle (MB). The end points of the study were (1) wheal and flare response of each device, with a dose-response curve, (2) the time required to apply each set of eight tests, and (3) the volunteers' subjective assessment of each device. On a different day, 10 of the volunteers were tested to determine the precision of each device. Dose-response curves for half-log dilutions of histamine phosphate were produced with a glycerosaline control. The DP and GP induced wheal and flare responses discernible from that of the glycerosaline control at a lower concentration of histamine phosphate than the MB and MT. The DP took a shorter time to apply eight samples than any other device. The MB was preferred by the most volunteers, but any device tested on the upper half of the back was usually preferred over that tested on the lower half. When 5 mg/ml histamine phosphate was used, coefficients of variation for each device demonstrated that for wheals the precision of the DP, GP, and MT was similar (mean, 21.1%, 23.1%, and 24.5%, respectively). The MB was larger (mean, 59.9%). For flares, the precision of GP and DP was similar (mean, 22.0% and 23.5%, respectively), with the MT and MB larger (mean, 35.5% and 58.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of six epicutaneous devices in the performance of immediate hypersensitivity skin testing

Six devices commonly used for immediate hypersensitivity epicutaneous skin testing were compared with regard to precision and diagnostic accuracy. Fifteen subjects were tested on the back to 10 mg/ml of histamine phosphate and 50% glycerosaline by prick technique with a smallpox needle (SN), bifurcated needle (BN), Greer "pen" (GP), and blood lancet, and by puncture with the Morrow-Brown needle (MB) and Multi-Test (MT). Five devices were tested in quintuplicate to histamine and once to glycerosaline in each subject; with MT, five histamine and three glycerosaline sites were used. Analysis of the wheal areas obtained with SN, BN, GP, and MB demonstrated comparable degrees of precision (coefficient of variation). The precision of MT was less than the other devices (p less than 0.05). The blood lancet demonstrated intermediate precision. Twenty-two of 45 (49%) of the glycerosaline skin tests performed with MT were falsely positive, significantly more than the other devices (p = 0.0001). We conclude that MB, BN, GP, and SP are comparable devices for use in immediate hypersensitivity skin testing. The low precision and reliability of MT used for testing on the back would appear to make this device less than adequate for diagnostic or research studies. Its high rate of false positive reactions requires caution in interpretation of results when it is used in the clinical diagnosis of allergy.

Circadian variation of skin reactivity and allergy skin tests

Previous investigations of the circadian variation in skin reactivity suggested that results of skin tests obtained in the afternoon could vary from the results obtained in the early morning and therefore could result in a differing assessment of patient sensitivity. To determine whether this was a practical concern in the normal clinical setting, we studied 20 adults and 20 children who had skin prick tests positive (3+ or more) to short ragweed. These patients were skin tested in duplicate at 8 AM and at 4 PM with fivefold serial dilutions of short ragweed extracts (1:20 to 1:12,500, wt/vol) and of histamine hydrochloride (10 to 0.016 mg/ml). Areas of wheal and flare were recorded and measured by computed planimetry. In addition, results were also read according to a conventional scoring system. Mean wheal and erythema areas with ragweed and histamine at each dilution were compared between morning and their corresponding evening values. Although there was a trend for the morning means to be larger than evening means, no significant differences between the two sessions were observed at any dilution. Mean morning skin index scores, as calculated from the combined mean wheal and erythema areas, were larger than mean evening scores for ragweed and histamine, but the differences were not of a degree to be clinically important. This observation was also true for conventional scores. Comparing the results from the two groups of children who had their first set of skin tests performed either in the morning or afternoon session indicated that there was no evidence of a refractory state of the skin during the second test sessions.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-mediated immunity assessed by skin testing (Multitest). II: Correlation between responses from arm and back

In 60 healthy adult volunteers and 58 patients with gastrointestinal disease a test system (Multitest) consisting of a plastic disposable multiple-puncture device capable of simultaneously applying seven delayed-type hypersensitivity antigens and a glycerin/saline diluent (negative control) was assessed. The Multitest device was applied on both the inner side of the forearm and on the back for assessment of cell-mediated immunity (CMI). The antigens used were two toxoids, tetanus and diphtheria, three bacterial antigens, Streptococcus, tuberculin and Proteus and two fungal antigens, Candida and Trichophyton. A scoring system based on both number and size of positive response revealed a median "score" on arm and back of 19 mm and 14 mm respectively, in the healthy volunteers and a median "score" of 12 mm and 8 mm respectively in patients with gastrointestinal disease. In both groups a significant difference was found between back and arm (P less than 0.01). The coefficient of determination (r2) shows that only 64% of the variability in scores on the back is explained by the regression line. Therefore, scores obtained from tests on the back cannot be interpreted with reference to normal values originating from tests applied to the inner side of the forearm.

Skin test reactivity to histamine from infancy to old age

The skin test reactivity to allergen and histamine differs according to the age of the patients, but complete data from infancy to old age are still lacking. Three hundred sixty-five subjects (1 to 85 years of age, 33.9% atopic, and 50.1% male patients) were prick tested with threefold dilutions of histamine hydrochloride (1 to 243 mg/ml). There was a significant (p less than 0.0001; F test) main effect of age on the skin reactivity to histamine. Age groups were defined and statistical analysis were performed by means of parallel line bioassay. All dose-response curves were linear and parallel. There is a significant increase in the mean wheal size between 4 to 5 and 6 to 9 years of age, 10 to 14 and 15 to 20 years. There was almost no difference between 15 to 20 and 21 to 50 years. No difference was observed between 21 to 30, 31 to 40, and 41 to 50 years, and then, the mean wheal sizes decreased significantly to reach a plateau after the age of 60 years. There was no sex difference, and skin tests with histamine were similar in atopic and nonatopic individuals.

Occupational asthma caused by isonicotinic acid hydrazide (INH) inhalation

Occupational asthma caused by isonicotinic acid hydrazide (INH) inhalation occurred in a 26-year-old female hospital pharmacist after symptoms of allergic rhinitis. Intradermal, inhalation, and Prausnitz-Küstner tests were performed with INH dissolved in saline, INH dissolved in the subject's serum and incubated at 25 degrees C for 4 hours, and an INH conjugate with human serum albumin. An INH conjugate with bovine serum albumin was also used in the prick tests alone. All preparations caused rapid positive skin reaction in the patient. Prausnitz-Küstner tests on the subject's mother were also rapidly positive. Furthermore, positive results were obtained not only in the inhalation tests with the three antigens but also in the environmental provocation tests. These results strongly suggested that the asthmatic symptoms of the subject were not caused by physical irritation from INH or other drugs and might be mediated by an IgE antibody specific to INH, a suggestion subsequently confirmed by in vitro enzyme-linked allergosorbent test for the antibody previously reported. This is the first precise description of INH-induced bronchial asthma, and the four kinds of INH preparations used in these tests might be very useful as tools of clinical diagnosis in INH allergy.

Diagnosis and immunotherapy of mould allergy. II. Reproducibility and relationship between skin sensitivity estimated by end-point titration and histamine equivalent reaction using skin prick test and intradermal test

To determine reproducibility and the optimal way of expressing skin sensitivity, simultaneous skin prick tests (SPT) and intradermal tests (ICT) were performed on 25 mould-allergic patients. The patients had a well-documented history of allergy to Cladosporium and Alternaria and were tested with partially purified standardized extracts of these two mould species. Skin prick tests were carried out on the volar side of the forearm and intradermal tests on the backs of the patients. The skin tests were performed as titration using quadruplicate determinations of 10-fold allergen dilutions. The area of the skin reactions measured by planimetry were plotted in a log-log system as a function of the allergen concentration. The reproducibility (SD/mean area X 100%) of the ICTs was significantly higher than that of the SPTs (17% versus 29%). A very low reproducibility was found with wheal areas less than 5 mm2. The dose response curve of the SPT wheal area was steeper than that obtained with ICT, both concerning ICT wheal and flare. Increasing the allergen concentration with a factor 10 resulted in a doubling of the wheal area in SPT, in contrast to a factor 1.7 using ICT. The coefficient of correlation using linear regression on the dose response curve was always higher than 0.9 with SPT and ICT wheal, but significantly lower with ICT flare. Skin sensitivity was estimated as end-point and histamine equivalent reaction. No significant correlation between SPT and ICT end-point titration was found contrary to the histamine equivalent reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Stabilization of a diluted aqueous mite allergen preparation by addition of human serum albumin. An intracutaneous test study

Stability of diluted Spectralgen Dermatophagoides farinae allergen preparations in phenol-saline with, and without human serum albumin (HSA) has been studied by intracutaneous tests in mite-allergic patients. The phenol-saline reconstituted mite allergen preparation lost activity to less than 1/10 of initial activity within 1 week, while mite allergen preparation reconstituted with solvent containing HSA was stable for at least 8 months after reconstitution. Human serum albumin probably prevents adsorption of allergens to glass surfaces which may be a problem for very diluted allergen preparations.