Sensitivity and specificity of specific IgE,skin prick test and atopy patch test in examination of food allergy

The aim of this study is the evaluation of the specificity and sensitivity of the skin prick tests (SPTs), specific IgE and atopy patch tests (APTs) in atopic dermatitis patients suffering from food allergy. A total of 301 patients were examined, complete dermatological and allergological examination was performed in all patients. The food allergy was confirmed to peanuts in 62 patients (20%), to egg in 16 patients (5%), to soy in 9 patients (3%), to wheat in 12 patients (4%) and to cow milk in 6 patients (2%). The specificity of SPT, specific IgE and APT is considered as good; the sensitivity of APT is low. The positive results in isolation cannot confirm the food allergy; however, together with other diagnostic methods, such as clinical history and open exposure test, these tests are valuable tool in examination of food allergy.     

The relationship between latex skin prick test responses and clinical allergic responses

BACKGROUND: Allergic responses to latex have been reported more frequently in the past 5 years. Although commercial skin prick test solutions are available and can be used in the diagnosis of latex allergy in some countries, the characteristics of patients sensitized to latex relative to their skin test responses have not been reported. OBJECTIVE: The purpose of this study is to relate the clinical characteristics of patients with latex sensitivity to the size of their latex skin prick test response. METHODS: A retrospective review of patients who were attending a hospital-based allergy and asthma clinic and who had positive skin test responses to a commercial latex skin test solution was undertaken. RESULTS: Of 47 patients who had skin test responses to latex, 36 had a mean wheal diameter at least 3 mm greater than the negative control (diluent). Sixty-eight percent were health care workers. There was a positive association between the size of skin test response and severity of latex-induced symptoms (p < 0.001). A history of banana sensitivity was also associated with larger skin test responses (p < 0.05). CONCLUSION: The size of the skin prick test response to latex solution that is commercially available in Canada reflects the severity of latex-induced clinical allergic responses. (J Allergy Clin Immunol 1996;97:1202-6.)     

Long-term repeatability of the skin prick test is high when supported by history or allergen-sensitivity tests: a prospective clinical study

BACKGROUND: Long-term reproducibility of the skin-prick test (SPT) has been questioned. The aim of the study was to investigate the clinical relevance of SPT changes. METHODS: SPT to 10 common inhalation allergens was performed annually from 1999 to 2001 in 25 nonsensitized and 21 sensitized subjects. An SPT was positive when > or =3 mm, and repeatable if either persistently positive or negative. Clinical sensitivity to birch pollen was used as model for inhalation allergy, and was investigated at inclusion and at study termination by challenge tests, intradermal test, titrated SPT and IgE measurements. Birch pollen symptoms were confirmed in diaries. RESULTS: The repeatability of a positive SPT was 67%, increasing significantly to 100% when supported by the history. When not supported by history, the presence of specific IgE was significantly associated with a repeatable SPT. Allergen sensitivity was significantly lower in subjects loosing SPT positivity. The repeatability of a negative test was 95%, decreasing significantly to 87% by the presence of other sensitization. Development of a positive SPT was clinically relevant. Elevation of SPT cut-off point did not enhance repeatability. CONCLUSION: SPT changes are clinically relevant. Further studies using other allergens are needed. Long-term repeatability of SPT is high in the presence of a supportive history.     

Combined skin prick and patch testing enhances identification of peanut-allergic patients with atopic dermatitis

BACKGROUND: Food atopy patch tests (APTs) are considered a useful tool for the diagnosis of food allergy. Hypersensitivity to peanuts has not been investigated by means of APTs so far. METHODS: APTs and skin prick tests (SPTs) with peanuts were performed in 136 atopic dermatitis (AD) patients. Relevance of positive and negative responses to these tests was assessed by repeated open challenges with peanuts. RESULTS: Nine percent of our AD patients reacted to the challenge. Positive responses to APTs were recorded in 19% of the patients, whereas in 12% positive SPTs were observed. APTs were more frequently positive in subjects with eczematous responses after challenge with respect to those with urticarial reactions. SPT reactivity proved to be higher in patients above 12 years of age, whereas APT positivity was more frequent in children under 6 years. APT sensitivity proved significantly higher than SPT sensitivity, in particular in children under 12 years of age. On the contrary, SPT specificity and positive predictive value were significantly higher with respect to those of APT in the age group of subjects under 6 years of age. CONCLUSIONS: Our data suggest that APTs with peanuts may represent a useful integration to standard testing modalities employed for the diagnosis of peanut allergy in AD patients.     

The predictive value of the skin prick test weal size for the outcome of oral food challenges

BACKGROUND: The skin prick test (SPT) is regarded as an important diagnostic measure in the diagnostic work-up of food allergy. Objective To evaluate the diagnostic capacity of the SPT in predicting the outcome of oral food challenges, and to determine decision points for the weal size and the skin index (SI) that could render double-blind, placebo-controlled food challenges unnecessary. METHODS: In 385 children (median age 22 months), 735 controlled oral challenges were performed with cow's milk (CM), hen's egg (HE), wheat and soy. Three hundred and thirty-six of 385 (87%) children suffered from atopic dermatitis. SPT was performed in all children. Diagnostic capacity, receiver-operator characteristics (ROC) curves and predictive decision points were calculated for the mean weal size and the calculated SI. RESULTS: Three hundred and twelve of 735 (43%) oral food challenges were assessed to be positive. Calculation of 95% and 99% predicted probabilities using logistic regression revealed predictive decision points of 13.0 and 17.8 mm for HE, and 12.5 and 17.3 mm for CM, respectively. However, using the SI, the corresponding cut-off levels were 2.6 and 3.7, respectively, for HE, and 2.7 and 3.7 for CM. For wheat, 95% and 99% decision points of 2.2 and 3.0 were found in children below 1 year of age. CONCLUSION: Predictive decision points for a positive outcome of food challenges can be calculated for HE and CM using weal size and SI. They may help to avoid oral food challenges.     

Prediction of challenge test results by flour-specific IgE and skin prick test in symptomatic bakers

Background:  Wheat and rye flours are among the most important allergens causing occupational asthma. Usually, the diagnosis of baker's asthma is based on inhalation challenge tests with flours.
Aims of the study:  To evaluate the relevance of flour-specific serum immunoglobulin E (IgE) and skin prick test (SPT) in the diagnosis of baker's asthma and to define flour-specific IgE concentrations and wheal sizes that allow a prediction of the outcome of challenge testing.
Methods:  Bronchial and nasal challenge tests with wheat (rye) flour were performed in 71 (95) symptomatic bakers. Determinations of flour-specific IgE as well as SPTs were performed in all subjects. Analyses included the calculation of sensitivity, specificity, positive (PPV) and negative predictive values (NPV) at different IgE concentrations and different wheal sizes, and receiver-operating characteristics (ROC) plots with the challenge result as gold standard.
Results:  Thirty-seven bakers were positive in the challenge with wheat flour, while 63 were positive with rye flour. Depending on the flour-specific IgE concentrations (wheal size), PPV was 74–100% (74–100%) for wheat and 82–100% (91–100%) for rye flour, respectively. The minimal cut-off values with a PPV of 100% were 2.32 kU/l (5.0 mm) for wheat flour and 9.64 kU/l (4.5 mm) for rye flour. The shapes of the ROC plots were similar for wheat and rye flour.
Conclusion:  High concentrations of flour-specific IgE and clear SPT results in symptomatic bakers are good predictors for a positive challenge test. Challenge tests with flours may be avoided in strongly sensitized bakers.     

上海地区过敏患者皮肤点刺试验临床分析

为了解上海地区过敏性疾病的主要过敏原,探讨过敏患者过敏原的分布情况及变化规律,收集1 407例过敏患者的皮肤点刺试验资料。结果显示,阳性率位于前五位的过敏原依次为粉尘螨64.89%、屋尘螨58.56%、热带螨40.58%、德国小蠊21.32%和美洲大蠊20.90%。以尘螨(粉尘螨、屋尘螨和热带螨)的阳性率最高。过敏患者对尘螨(粉尘螨、屋尘螨和热带螨)、蟑螂(德国小蠊和美洲大蠊)、狗毛屑、猫毛屑及虾过敏与年龄有关。呼吸道过敏性疾病患者对尘螨、蟑螂、狗毛屑、猫毛屑和花粉过敏的阳性率均明显高于过敏性皮肤病患者(P<0.05)。提示上海地区以尘螨为主要过敏原,对尘螨、蟑螂、狗毛屑、猫毛屑及虾过敏与患者年龄有关,但与性别无关。呼吸道过敏性疾病患者较过敏性皮肤病患者有更高的阳性率。     

Influence of skin prick test criteria on estimation of prevalence and incidence of allergic sensitization in children

In a prospective cohort study on atopy in childhood, three skin prick tests (SPT) were performed in 1135 primary schoolchildren over a 2–year period. We studied the development of average sizes of allergen wheals in reactive children and of average sizes of histamine wheals in all children, and we investigated the influence of choice of SPT criterion on the prevalence and incidence of sensitization. A year-to-year increase of average allergen wheal sizes as well as of average histamine wheal sizes was observed. These increases seemed to be related to the natural growth of the children. Furthermore, an observer bias effect of the person who did the pricking on average wheal sizes was found. There were considerable differences in estimations of prevalences and incidences depending on the definition of SPT criterion. Estimations using a criterion based solely on the allergen wheal size were affected by variation of allergen wheal sizes caused by growth and observer effects. The ratio criterion was not influenced by observer effects, nor did it seem to be affected by aging effects. In conclusion, our data suggest that the ratio criterion, which relates the size of the allergen wheal to the size of the histamine wheal, is the most appropriate SPT criterion because it is not affected by growth of allergen wheals in childhood and it appears to compensate for possible observer bias.     

Allergy screening including a comparison of prick test results with allergen-coated lancets (Phazet®) and liquid extracts

During an allergy screening of families with a history of allergy in one or more subjects, skin prick tests (SPT) were performed in duplicate in 314 adults. The tests were performed with a new type of lancet with a 0.9 mm long point, loaded either with allergen (Phazet) or used together with standardized extracts (10,000 and 100,000 BU/ml). Wheals obtained with both methods were compared, and related to total IgE concentrations and history. A wheal area of 3 and 7 mm2 was used as cut-off limit. Results with Phazet were close to those with Pharmalgen 100,000 BU/ml. With both methods precision was good for allergens, but less for Phazet histamine than for the corresponding wet test. SPT results obtained with Phazet and 100,000 BU/ml correlated better with history than the results with 10,000 BU/ml. Using a wheal size of 7 mm2 as cut-off limit the efficiency for five tested allergens was 91%. "False positive" tests, possibly indicating an unobserved or latent type of allergy, were found more often with higher serum IgE concentrations. The safety of SPT was confirmed and Phazet was well accepted by nurses and tested subjects.     

Evaluation of the prevalence of skin prick test positivity to Alternaria and Cladosporium in patients with suspected respiratory allergy

D'Amato G, Chatzigeorgiou G, Corsico R, Gioulekas D, Jäger L, Jäger S, Kontou-Fili K, Kouridakis S, Liccardi G, Meriggi A, Palma-Carlos A, Palma-Carlos ML, Pagan Aleman A, Parmiani S, Puccinelli R Russo M, Spieksma FThM, Torricelli R, Wüthrich B. Evaluation of the prevalence of skin prick test positivity to Alternaria and Cladosporium in patients with suspected respiratory allergy. A European multicenter study promoted by the Subcommittee on Aerobiology and Environmental Aspects of Inhalant Allergens of the European Academy of Allergology and Clinical Immunology.
This trial was undertaken to study, in several geographically spread European countries, the prevalence of skin prick test (SPT) positivity to Alternaria (A) and Cladosporium (C) in subjects with nasal and/or bronchial symptoms of suspected allergic cause. Each patient completed an anamnestic questionnaire and underwent SPT with a panel of common inhalant allergens and also A and C supplied by three different laboratories, to allow for manufacturer bias. Specific scrum IgE determination was carried out only in subjects with SPT positivity to A and/or C with an immunoassay system. In nine European allergology centers, a total of 877 subjects was enrolled in the trial; 83 of them showed SPT positivity to A and/or C; only nine patients showed monosensitization to A , and none to C The highest percentage of positive subjects was found in Spain (20%); the lowest in Portugal (3%). In the other seven centers, the variation was 7–10%. The age range of mold-positive subjects was 5–60 years. Rhinitis was by far the most common symptom, whether associated or not with asthma and/or conjunctivitis.     

Reproducibility of skin prick test results in epidemiologic studies: a comparison of two devices

The reproducibility of skin prick tests under field conditions is essential for comparing prevalences between centers in epidemiologic multicenter studies. This study aimed to evaluate and compare the reproducibility of two widely used skin prick test devices: the Multi-Test and the ALK lancet. The subjects were 28 children, aged 6–14 years, with known sensitivities Dermatophagoides pteronyssinus (D. pter). Both devices were applied to each subject on two occasions, 1 week apart, by different, randomly assigned fieldworkers, using histamine, negative control, and the D. pter. allergen extract. For all three tested solutions, mean wheal sizes were larger for the Multi-Test than for the ALK lancet. The coefficient of variation for histamine was 21.8% for the Multi-Test and 17.3% for the ALK lancet. The coefficients of variation for the allergen D. pter. amounted to 47.4% for the Multi-Test and to 24.6% for the ALK lancet. The percentage of concordant test results was 92.6% for the Multi-Test and 100.0% for the ALK lancet for a cutoff point of wheal size equal to or greater than 1 mm. The results of this study suggest that the single ALK lancet performs slightly better than the Multi-Test device with respect to reproducibility under conditions of epidemiologic field studies.     

Wheat allergy: diagnostic accuracy of skin prick and patch tests and specific IgE

BACKGROUND: Food allergy makes an important contribution to the pathogenesis of atopic eczema in infants. However, clinical data on cereal allergy are scanty. The objective was to study the relevance of patch testing, skin prick tests, and the concentration of wheat-specific IgE antibodies (CAP RAST) in correlation with oral wheat challenge in infants with suspected wheat allergy. In particular, we aimed to determine whether the patch test could increase the diagnostic accuracy in detecting wheat allergy. METHODS: The study material comprised 39 infants under the age of 2 years. Of these patients, 36 were suffering from atopic eczema and three had only gastrointestinal symptoms. The patients were subjected to a double-blind, placebo-controlled or open wheat challenge. Wheat-specific IgE was measured by CAP RAST, and skin prick and patch tests were performed. RESULTS: Of the total 39 wheat challenges, 22 (56%) were positive. Of the positive reactions, five involved immediate-type skin reactions over a period of 2 h from the commencement of the challenge. In 17 patients, delayed-onset reactions of eczematous or gastrointestinal type appeared. Of the infants with challenge-proven wheat allergy, 20% showed elevated IgE concentrations to wheat, 23% had a positive skin prick test, and 86% had a positive patch test for wheat. The specificities of CAP RAST, skin prick tests, and patch tests were 0.93, 1.00, and 0.35, respectively. CONCLUSIONS: Our study demonstrated that patch testing with cereals will significantly increase the probability of early detection of cereal allergy in infants with atopic eczema and is helpful in the planning of successful elimination diets before challenge. The specificity of the patch test was lower than that of other tests. Therefore, confirmation of the diagnosis with the elimination-challenge test is essential in patients with positive patch test results.     

Correlations between skin prick tests using commercial extracts and fresh foods, specific IgE, and food challenges

The skin prick test is the most widely used test for detecting IgE-mediated food hypersensitivity. Our study aimed to define firstly the correlations between results obtained with prick tests using commercial extracts and fresh foods, and secondly the correlations between these results and those obtained with labial and/or oral challenge. We compared the wheal diameters read at 15 min with commercial extracts and fresh foods, for four foods, in 430 children with suspected food allergy. For cow's milk, wheal diameters were larger with commercial extracts, but the difference was not significant. Conversely, wheal diameters were significantly larger with fresh foods for the other food allergens. Skin prick tests were positive in 40% of cases with commercial extracts and in 81.3% with fresh foods. The overall concordance between a positive prick test and positive challenge was 58.8% with commercial extracts and 91.7% with fresh foods. These results indicate that fresh foods may be more effective for detecting the sensitivity to food allergens. Fresh foods should be used for primary testing for egg, peanut, and cow's milk sensitivity.     

Atopy patch test in examination of food allergy in patients suffering from atopic dermatitis

Aim: The evaluation of the importance of atopy patch tests in patients suffering from food allergy to egg’s white and yolk, peanuts, soy, cow’s milk and wheat. Methods: 240 patients were examined. Complete dermatological and allergological examination was performed in all patients including specific IgE, skin prick test, atopy patch test and the challenges tests. Results: The specificity of atopy patch tests is for soy 96%, for egg 95%, for wheat 95%, for peanuts 99% and for milk 99%. The sensitivity of atopy patch tests is for soy 62%, for egg 35.7%, for wheat 16.7%, for peanuts 20.8% and for milk 50%. Conclusion: The specificity of atopy patch tests may be considered good; regarding the sensitivity, the high percentage of false negative results should make us believe that these tests are not conclusive.