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.     

"Atopy patch tests" in the diagnosis of delayed food hypersensitivity

The prevalence of atopic diseases is increasing worldwide. Food allergies are the earliest manifestation of atopy. Atopic eczema affects about 18% of infants in the first 2 years of life and the main cause is allergy to multiple foods. A strong association has been shown between atopic eczema and IgE mediated allergy to milk, egg or peanut, but more than two-thirds of patients intolerant to food proteins have no evidence of IgE sensitization to the relevant food protein. Recently, patch testing with proteins has been found to be helpful in diagnosing food allergy in cases where skin prick tests and estimation of specific antibodies have failed. The methodology of atopy patch test (APT) is unstandardized, and contradictory results have been reported. In contrast to the more standardized APT methodology with aeroallergens, the sensitivities and specificities of food allergens can easily be estimated with food challenge tests. With multiallergic children adding of APTs to the skin prick tests and specific antibody estimation tests give more information for planning a wide enough elimination diet to get the skin and gastrointestinal tract symptomless in order to perform the challenge test which remains the only reliable test for food allergy. Standardization of the APT materials and reading procedure will add to the reliability of this new test method.     

Atopic eczema and allergy

Although the pathomechanisms of respiratory atopy are well established, the role of IgE-mediated hypersensitivity in the elicitation and maintenance of eczematous skin lesions in atopic eczema (AE) is still controversial. There is, however, evidence for exogenous elicitation of AE by contact with aero- or food allergens (house dust mite, cat, and so forth). Recent investigations show that epidermal Langerhans’ cells bind IgE via different receptors, especially the high-affinity receptor (FcεRI), which is significantly more strongly expressed in lesional skin of AE compared with other inflammatory skin diseases including allergic contact dermatitis. The clinical relevance of IgE-mediated sensitization in AE has been evaluated by the so-called atopy patch test (APT). The APT shows a much higher specificity compared with the skin prick test and radioallergosorbent test. However, allergic reactions do not play a decisive role in every case of AE. Other factors, such as nonspecific skin irritability or psychosomatic interactions, have to be considered. The concept of “extrinsic” versus “intrinsic” types of AE seems attractive. The concept of AE starting with T_H2 inflammation, becoming T_H1 inflammation in chronicity, and finally progressing to an autoimmune disease with IgE antibodies against autologous epidermal proteins is very attractive. Based on new knowledge, new methods in diagnosis, treatment, and prevention will develop, including more effective avoidance strategies, more potent anti-inflammatory treatment (eg, immunomodulation or topical immunophyllins), and new ultraviolet modalities. The new findings have given rise to a possible new classification of eczema/dermatitis. The concept of “patient management,” including all aspects from avoidance to therapy, has gained acceptance.     

Reproducibility and use of low-concentration skin prick test.

We aimed to evaluate the reproducibility of the skin prick test performed with serial 1:4 dilutions of commercial standardized extracts in comparison with serum-specific IgE and the undiluted commercial extract. Twenty-four subjects sensitized to one (17 cases) or two (seven cases) inhalant allergens were selected and submitted to duplicate skin prick tests with concentrated commercial allergenic extracts or with serial 1:4 dilutions of the same extracts in two different examinations 7 days apart. Blood samples were obtained from 17 of the 24 patients for specific IgE determination. No statistically significant within-patient variations in the area of the wheal in skin prick tests done 1 week apart were found up to the eighth dilution (1:256) of the commercial allergen. On a patient-by-patient basis, only some dilutions showed a statistically significant correlation between allergen-specific IgE and the wheal area elicited by the same allergen, and a significant correlation was found between the wheal elicited by 10 mg/ml histamine and both the concentrated and diluted allergens (up to the sixth dilution). In polysensitized patients, the allergen producing the largest wheal when used in concentrated form did not produce the same result when diluted. The skin prick test with low-potency allergens was reproducible in individual patients even after a 7-day interval up to a 1:256 dilution of the commercial extract, although there was no clear correlation with allergen-specific IgE concentration. In polysensitized patients, the use of high-potency or low-potency allergens for skin prick tests can lead to different conclusions regarding the relative importance of each allergen.     

The role of food allergy in atopic dermatitis

Atopic dermatitis (AD) is a chronic, pruritic, inflammatory skin disease affecting more than 10% of all children. Sensitization to foods triggers isolated skin symptoms in about 30% of children. These symptoms include immediate reactions within minutes after ingesting food without exacerbation of AD and early and late exacerbations of AD. It is important to identify clinically relevant sensitizations to foods using skin prick tests, a specific IgE blood test (ImmunoCAP; Phadia, Portage, MI, USA), and double-blind, placebo-controlled food challenges to initiate appropriate dietary interventions and avoid unnecessary dietary restrictions. Children with AD triggered by food allergens demonstrate a distinct immune response upon stimulation of their peripheral blood mononuclear cells with food allergen. A defective skin barrier and increased intestinal permeability appear to facilitate allergen sensitization. Appropriate skin care to maintain skin barrier function and dietary avoidance of highly allergenic foods during infancy may help to prevent allergen sensitization, thereby reducing the severity of AD and food allergies.     

Sensitivity and specificity of food specific IgE and IgG determinations for the diagnosis of food allergy

Among the methods currently used to demonstrate a sensitization to foods, the measurement of food specific IgE antibodies (sIgE) is the most practical but not the most accurate. The "sensitivity" of food sIgE determinations is, for example, suboptimal with unstable allergens in fruits and vegetables that are involved in the (birch) pollen-related immediate oral allergy syndromes. In this particular syndrome the history is often conclusive and can be substantiated by skin prick tests with fresh foods. The "sensitivity" of sIgE tests is much better when sIgE are directed to stable plant or animal food allergens which often cause non-immediate generalized reactions. Foods, usually, contain many different (glyco)proteinic allergens of which some are stable and others not. The "sensitivity" of the sIgE test with a particular food, therefore, varies according to the type of allergen that is recognized by the patient. The "specificity" of sIgE tests with foods is affected by the existence of homologous food allergens which induce cross-reactive IgE that may or may not be clinically relevant. While variable, clinical cross-reactivity is more common among botanically-related fruits, among different nuts, among mammalian foods and among seafood than among cereals, grains and legumes. The "specificity" of food sIgE tests is much better when sIgE are directed to unique non-cross-reactive food allergens. Unfortunately, neither the presence of food sIgE nor its level are predictive of clinical reactivity. The identification of individual allergens in foods and the characterization of the relevant IgE binding sites in these allergens might lead to the development of tests that only measure sIgE to clinical relevant food allergens.     

Specific IgE to Common Food Allergens in Children with Atopic Dermatitis

Background: Atopic dermatitis is a major public health problem, often starting in early childhood and sometimes followed by other allergic diseases. Although hypersensitivity to foods is assumed to play an essential role in the development of atopic dermatitis in some patients, little is known about common food allergens in Iranian children with atopic dermatitis. Objectives: This study was designed to identify probable food allergens in Iranian children with atopic dermatitis and find the relationship between food sensitization and the severity of atopic dermatitis. Methods: This study included 90 children aged 2-48 months with atopic dermatitis. Skin prick tests for cow's milk, hen's egg, almond, potato and soybean were done. Serum specific IgE to 20 food allergens was also screened. Results: Among children with atopic dermatitis, the frequency of food sensitization was 40% by skin prick test and 51% by food-specific IgE. Children with atopic dermatitis were most commonly sensitized to cow's milk (31%), hen's egg (17.7%), tree nuts (17.7%), wheat (12.2%), potato (11.1%), tomato (8.8%) and peanut (8.8%). In 42 children with moderate to severe eczema, sensitivity to food allergens was 78.5% by skin prick test and 88% by serum specific IgE evaluation. Conclusion: Our results showed that cow's milk, hen's egg and tree nuts were the most common food allergens in Iranian children with atopic dermatitis. Sensitization to foods was much higher in patients with moderate to severe atopic dermatitis. Determining specific IgE in children with atopic dermatitis can be helpful in managing these patients.     

Component-Resolved Diagnosis for Phleum Allergy: The Role of Recombinants

Background. Conventional diagnostic tests (such as radioallergosorbent test [RAST] and skin prick test [SPT]) use native raw pollen allergen extracts to establish allergy. However, recombinant allergens may offer important advantages compared with their natural counterparts. Objective. This study evaluated serum immunoglobulin E (IgE) in patients with grass-induced allergic rhinitis (AR) or AR with asthma (ARA), comparing assays with natural or recombinant grass allergens. Methods. Sixty patients (33 AR, 27 ARA) positive with SPT and serum IgE for Phleum pratense were enrolled in the study. Serum IgE specific for conventional and recombinant Phleum pratense: rPhl p 1, rPhl p 2, nPhl p 4, rPhl 5b, rPhl p 6, rPhl p 7, rPhl p 11, rPhl p 12, were measured by the IFMA procedure (ImmunoCAP, Phadia, Uppsala, Sweden). Data were expressed as the median (md) and percentiles. Recombinant allergen results were expressed also as the percentage of positive concentrations. The Wilcoxon test was used to compare samples. Because diagnosis is a binary variable (AR/ARA), logistic regression analysis was performed to identify possible correlates. Results. IgE concentrations assessed with recombinant allergens were significantly higher in ARA patients (p = .05) than in AR patients. A value >5.8 kU/L is the optimal cut-off to discriminate AR and ARA patients. Model specificity was 76%, sensitivity 78%, and efficiency 77%. Conclusion. This study shows that IgEs for natural and recombinant grass pollen allergens are significantly higher in patients with AR and asthma. Moreover, using recombinant allergens it is possible to define a prediction model for diagnosis with 77% efficiency. Therefore, this study may suggest that there are advantages of using recombinant or purified, native allergens over crude extracts.     

Dissecting the causes of atopic dermatitis in children: less foods, more mites

Atopic dermatitis (AD) is a common, chronic or chronically relapsing, multifactorial skin disease that mainly occurs in children but affects also adults. AD usually begins early in life and often concerns people with a personal or family history of asthma and allergic rhinitis. AD is characterized by eczematous changes in the epidermis and originates from a late, T-cell mediated reaction associated to the formation and production of memory T-cell of TH2 type, occurrence of homing receptor at skin level and cutaneous lymphocyte-associated (CLA) antigens. Extrinsic or allergic AD, but not intrinsic AD, shows high total serum IgE levels and the presence of specific IgE for environmental and food allergens. A pivotal role in the pathogenesis of AD is played by filaggrin, a protein contained in the granular layer of the epidermis regulating the aggregation of keratin filaments. Mutation in the filaggrin gene causes decreased barrier function of the corny layers of the epidermis. This favours the enter through the skin of environmental allergens, especially the house dust mite, that further facilitates such entering by the proteolytic activity of its major allergen Der p 1. In fact, recent advances suggest that the dust mite, more than foods, is the major cause of allergic AD. As far as the causal diagnosis of AD is concerned, there is notable evidence supporting the capacity of the atopy patch test (APT) to reproduce the pathophysiologic events of AD. This makes APT a valuable diagnostic tool for AD.     

Atopy patch test in children with cow's milk and hen's egg allergy: Do clinical symptoms matter?

Introduction and objectivesSince early 2000s, atopy patch test (APT) has been used to determine non-IgE and mixed-type food allergies. Previous studies have reported conflicting results about the diagnostic value of APT in food allergies, due to non-standardized methods.We aimed to determine the diagnostic efficacy of APT compared to open oral food challenge (OFC) in patients diagnosed with cow's milk allergy (CMA) and hen's egg allergy (HEA) manifesting as atopic dermatitis (AD) and gastrointestinal system symptoms.Materials and methodsIn patients with suspected AD and/or gastrointestinal manifestations due to CMA and HEA, the results of OFC, APT, skin prick test (SPT) and specific IgE (sIgE) were reviewed. Specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of sIgE, SPT, APT and SPT + APT were calculated.ResultsIn total 133 patients with suspected CMA (80) and HEA (53) were included in the study.In patients with CMA presenting with gastrointestinal symptoms, APT had sensitivity of 9.1%, specificity of 100%, PPV of 100% and NPV of 48.7%. In atopic dermatitis patients, sensitivity of APT was 71.4%, specificity 90.6%, PPV 62.5% and NPV 93.6%.In patients diagnosed with HEA, the sensitivity, specificity, PPV and NPV values of APT were 72.0%, 78.6%, 47.2% and 75.0%, respectively. In patients diagnosed with HEA presenting with AD, sensitivity of APT was 87.5%, specificity 70.6%, PPV 73.7% and NPV 85.7%. Atopy patch test had lower sensitivity (44.4%) and higher specificity (90.9%) in patients diagnosed with HEA presenting with gastrointestinal symptoms than those presenting with AD.ConclusionOur study showed that APT provided reliable diagnostic accuracy in atopic dermatitis patients. However, APT had low sensitivity in patients with gastrointestinal symptoms.     

In vitro diagnostic evaluation of patients with inhalant allergies: summary of probability outcomes comparing results of CLA- and CAP-specific immunoglobulin E test systems.

For the diagnosis of allergy, presence of allergen-specific immunoglobulin E (IgE) usually is established either by allergen skin tests or by in vitro allergen-specific IgE measurements. However, in vitro assays of specific IgE often are modified as manufacturers improve allergens or change reagents to optimize test performance, affecting the diagnostic performance of in vitro allergen-specific IgE assays. This investigation compares the diagnostic outcomes of the Hitachi Chemical Diagnostics chemiluminescent assay (CLA) and Pharmacia, capsulated hydrophilic carrier polymer (CAP) in vitro allergen-specific IgE test methods in patients with inhalant allergy to a panel of selected allergens. Sera were obtained from 60 consecutive patients who had a clinical history suggesting inhalant allergy and were evaluated by allergen skin-prick test (SPT). Only patients with clinical findings of allergic asthma or rhinoconjunctivitis were included. Sera from patients with at least one positive SPT, which clinically correlated with the case history, were used for specific IgE measurements. Sensitivity and specificity were defined as conditional probabilities describing performances of the CAP system and the CLA system in reference to a standard composed of a combination of allergen-specific symptoms and a positive SPT. A test concordance of 79% was found between the CLA and CAP test results with a correlation coefficient of 0.8. Allergen-specific IgE assay sensitivity of the CLA and CAP systems was similar and allergen dependent, ranging from 67 to 100%. Assay specificity ranged from 39 to 86% for the CLA system and from 36 to 81% for the CAP system. When comparing the specific IgE results with allergen SPTs, 75% (+/- 3%) of CLApositive patients had a positive SPT, and 92% (+/- 4%) of CAPpositive patients had a positive SPT. Eighty-four percent (+/- 4%) of CLAnegative patients had a negative SPT, whereas 69% (+/- 5%) of CAPnegative patients had a negative SPT. The overall concordance between skin tests and in vitro tests was 76% for CLA and 67% for CAP. CLA and CAP score values showed good correlation and both tests may be useful when skin tests cannot be performed to identify subjects with IgE-mediated allergy. The CLA and CAP assays for allergen-specific IgE may be useful as part of an initial allergy evaluation because of the high negative predictive value of negative test results. For the majority of allergens the sensitivity was high. However, the specificity of both in vitro tests was low, indicating that positive in vitro test results should be evaluated carefully in conjunction with clinical symptoms and allergen-specific skin tests to determine the clinical relevance of the allergen sensitization.     

Age, gender and reactivity to allergens independently influence skin reactivity to histamine.

BACKGROUND. The ability to mount an IgE response to allergens is a prerequisite for the development of positive allergen skin tests. Histamine is commonly used as a positive control in skin prick testing and provides a measure of nonspecific skin reactivity, similar to bronchial hyper-responsiveness. METHODS. To determine whether allergen responsiveness, age, gender and season of the year contribute to histamine sensitivity, 620 subjects (502 of them with at least one known sensitizing allergen and the remaining 118 non-allergic controls) were prick-tested with a panel of allergens common in the Northern Italy semi-rural area where the patients lived, and with 10 mg/ml histamine dihydrochloride. RESULTS. We found higher histamine reactivity in allergic versus control individuals (median value 23.7 versus 19.8 mm2; p=0.0497). Likewise, we found in allergic subjects a correlation between allergen responsiveness in terms of number of positive allergens at skin prick test and sensitivity to histamine (mono- sensitized versus poly-sensitized subjects: p=0.0015). Moreover older age and male sex were associated with a higher response to histamine, also when separately considering allergic subjects (p<0.0001 in both cases: correlation coefficient for age versus histamine reactivity: r=0.3408). The correlation between allergen responsiveness and sensitivity to histamine was maintained also when statistically balanced for age and sex. CONCLUSION. Allergen responsiveness, gender and age allow more accurate prediction of histamine sensitivity than either parameter alone.     

呼出一氧化氮监测联合变应原皮肤点刺试验在儿童哮喘诊治中的应用性研究

目的 研究呼出一氧化氮监测联合变应原皮肤点刺试验在儿童哮喘诊治中的应用价值.方法 选取72例哮喘患儿与同期72例正常儿童,对比其呼出一氧化氮指标及哮喘患儿变应原皮肤点刺试验结果;观察患儿治疗前后呼出一氧化氮变化情况.结果 治疗前患儿组呼出气一氧化氮浓度明显高于正常组,治疗后该浓度明显下降;患儿对12种变应原均存在一定程度的过敏反应,其中屋尘螨及粉尘螨总阳性率最高.结论 呼出一氧化氮及变应原皮肤点刺试验能够有效指示儿童哮喘的发生,在指导治疗中起到关键作用.     

Sensitivity of the skin prick test and specificity of the serum-specific IgE test for airway responsiveness to house dust mites in asthma.

BACKGROUND: The concept that asthma diagnosis based on allergen-specific IgE levels in serum is more accurate than diagnosis based on skin test reactivity is controversial. OBJECTIVE: To determine the atopy parameter that correlates most closely with airway reactivity to house dust mites in asthma. METHODS: Forty-three asthma cases were examined retrospectively for data on Dermatophagoides farinae-specific bronchoprovocation, serum-specific IgE, and skin prick tests. RESULTS: The maximal decreases in FEV1 following bronchoprovocation were correlated significantly with both the IgE levels and skin test scores. The accuracies of the tests were highest at a cutoff value of class 4 or higher for the IgE and of 3+ or higher for the skin test. At the cutoff values, the accuracies of both tests were similar (70% vs. 70%). The sensitivity of the skin test (81%) was higher than that of the IgE test (67%), whereas the specificity of the IgE test (71%) was higher than that of the skin test (52%). The sensitivity of the skin test was 91% at 2+ or higher, and the specificity of the IgE test was 95% at class 6 or higher. CONCLUSION: These results suggest that both the specific IgE level and the skin test reactivity are useful parameters in the prediction of positive airway responses to house dust mites in asthma. However, the skin test is more sensitive, whereas the IgE test is more specific. Therefore, these tests can be used in a complementary fashion (i.e., the skin test for screening and the specific IgE test for confirmation of the relevant allergen).     

Molecular diagnosis of allergy to Anisakis simplex and Gymnorhynchus gigas fish parasites

BackgroundThere has been an increase in the prevalence of hypersensitivity to Anisakis simplex. There are fish parasites other than Anisakis simplex whose allergenicity has not yet been studied.ObjectiveTo assess IgE hypersensitivity caused by fish parasite allergens in patients with gastro-allergic symptoms after consumption of fish, shellfish or cephalopods, compared with healthy subjects, pollen allergic individuals and children with digestive symptoms after eating marine food.MethodsWe carried out in vivo tests (skin prick) and in vitro tests (specific IgE determination, Western blot) and component resolved diagnostics (CRD) using microarray analysis in all patients.ResultsCRD better detected sensitisation to allergens from marine parasites than skin prick tests and determination of specific IgE by CAP. Sensitisation to Gymnorhynchus gigas was detected in 26% of patients measured by skin prick tests and 36% measured by IgE.ConclusionsThe prevalence of hypersensitivity to marine parasite allergens other than Anisakis simplex should be studied, and the most appropriate technique for this is CRD.     

Sensitivity and exposure to indoor allergens in adults with differing asthma severity.

In asthma, it is uncertain whether there is an association between degrees of exposure to domestic allergens and asthma severity. The pattern of sensitivity and exposure to common indoor allergens was examined in subjects with differing asthma severity. Sensitivity to house dust mite, dog and cat allergen and exposure to Der p 1, Can f 1 and Fel d 1 were assessed by skin prick tests and settled dust analysis in 28 subjects with severe asthma and 28 age- and sex-matched subjects with mild asthma (two declined skin prick test). All severe asthmatic subjects had at least one positive skin test and 20 of the 28 subjects were positive to all three allergens. Fourteen of the 26 subjects with mild asthma who took skin prick tests were positive to at least one, and one of these subjects was positive to the three allergens tested. Except for bedroom Fel d 1, the proportion of severe asthmatics both sensitized and exposed to each allergen at each site was significantly greater than the proportion sensitized and exposed in the mild asthma group. The geometric mean allergen concentrations, with the exception of bedroom Fel d 1, were greater in sensitized severe asthmatics than the sensitized mild asthmatics, which was significant for Der p 1 in bedroom samples and Can f 1 in bedroom and living room samples. These results support an association between the degrees of domestic allergen exposure in sensitized individuals and asthma severity.     

Egg and milk allergy in asthmatic children: assessment by immulite allergy food panel, skin prick tests and double-blind placebo-controlled food challenges

There is a perception that asthmatic symptoms may be worsoned by ingestion of certain foods. This study aimed to investigate whether ingestion of cow's milk or egg might induce respiratory symptoms in asthmatic children. Fifty asthmatic children aged 1.5 to 6 years old, with positive Immulite Food Panel FP5 test results were included in the study. Fifty healthy children within the same age group were accepted as control group. Total serum IgE levels were measured and skin prick tests for food allergens including milk and egg were performed. All of the subjects underwent oral, double-blind, placebo-controlled challenge with fresh egg and cow's milk powder. Two medical histories were confirmed by double-blind, placebo-controlled challenge in 9 patients (22.2%). Skin prick tests were positive in 9 patients (18%) with milk and 18 patients (36%) with egg antigen. Two children experienced wheezing, one after ingesting milk and the other after egg challenge (4%). In the control group no positive reactions were seen with egg or milk challenges. Our findings confirm that food allergy can elicit asthma in children, but its incidence is low, even with major allergens such as egg and milk. History, specific IgE determinations and skin prick tests are not reliable in diagnosing food reactions. Since any diet can cause rapid deficiencies in infancy, diet restrictions must not be applied, without performing double-blind, placebo-controlled challenge.     

Differential IgE reactivity to Der p 1 and Der p 2 allergens of Dermatophagoides pteronyssinus in mite-sensitized patients.

Several studies have shown that the presence of IgE antibodies to house dust mites (HDM), particularly Dermatophagoides pteronyssinus (Dpt), is an important risk factor for asthma. Allergen immunotherapy is indicated for patients with IgE antibodies to clinically relevant allergens. The aims of this study were to analyze the levels of specific serum IgE to Der p 1 and Der p 2 allergens in mite-sensitized atopic patients and to compare them with both in vivo (skin prick test) and in vitro (IgE-ELISA) sensitizations to Dpt crude extract. Forty-seven atopic patients with allergic rhinitis with or without intermittent or persistent mild asthma and positive skin prick test (SPT) to Dpt total extract were studied. Thirty age-matched healthy subjects with negative SPT to HDM were included as controls. Levels of total IgE and Dpt-, Der p 1- and Der p 2-specific IgE were measured by ELISAs in SPT-positive atopic patients and SPT-negative control subjects. Among 47 symptomatic atopic patients, 27 (57.4%) were double positive IgE to Der p 1 and Der p 2 allergens, 3 (6.4%) were single positive IgE to Der p 1, 4 (8.5%) were single positive IgE to Der p 2, and 13 (27.6%) were double negative IgE to both allergens. There was a significant correlation between Der p 1- and Der p 2-specific IgE levels, but not between Der p 1- or Der p 2-IgE levels and SPT results. The double negative IgE patients had the smallest skin test reactions although they showed high mean levels of total serum IgE. Therefore, the knowledge of specific IgE levels to Der p 1 and Der p 2 major allergens might support physicians for indication or follow-up in mite-sensitized patients under allergen-specific immunotherapy. These approaches might be important for obtaining improved safety and efficacy of the current clinical practice of allergen immunotherapy.     

Overview of Serological-Specific IgE Antibody Testing in Children

Allergic diseases are among the most common chronic conditions in the pediatric population. Allergy diagnostic testing is an important part of the evaluation/management of allergic patients because the history may not be precise enough to identify the specific allergen sensitivity. In addition to providing information about specific sensitivities, allergy diagnostic tests have some predictive value in terms of future risk of developing an allergic condition and the severity/persistence of the allergic disease. The two most commonly used methods of confirming allergen sensitization are skin testing and measurement of serum-specific IgE. Both methods have similar diagnostic value in terms of sensitivity and specificity, with both parameters varying with the clinical scenario and allergen tested. Currently, there are three US Food and Drug Administration–cleared, serum-specific IgE assays used in the United States. The three assays report comparable analytic sensitivity, with the coefficients of variation of the precision, reproducibility, and linearity being less than 15%. However, comparative studies have demonstrated significant inter-assay variability, suggesting that they detect different populations of IgE antibody in human sera or do not measure the same antibodies with the same efficiency. Current specific IgE assays utilize allergen extract reagents. Testing with these reagents may identify sensitivity to clinically irrelevant allergens. This diagnostic limitation has spurred the development of molecular diagnostic tests, also referred to as component-resolved diagnostics, which utilize purified native or recombinant allergens to detect IgE sensitivity to individual allergen molecules. These advancements in serum IgE testing may enhance the precision of allergy diagnostic testing, which may decrease the need for oral food challenges and improve the specificity of allergen immunotherapy.     

How necessary are specific IgE antibody tests in allergy diagnosis?

In a 12-month study 301 patients referred to hospital consultants with putative allergic symptoms were tested for specific IgE antibodies to a panel of allergens and for total serum IgE levels. Examination of the data in relation to clinical information and the results of skin prick tests showed that the specific IgE antibody test has a limited role in the investigation of such patients.