Comparison of skin prick test results between crude allergen extracts from foods and commercial allergen extracts in atopic dermatitis by double-blind placebo-controlled food challenge for milk, egg, and soybean

Evaluation of Skin Prick-Test Reactions for Allergic Sensitization in Dogs With Clinical Symptoms Compatible With Atopic Dermatitis. A Pilot Study

Skin prick-test is the first choice for the detection of type I hypersensitivity in human atopic dermatitis. Canine atopic dermatitis resembles several symptoms of the disease in the human counterpart. In canine atopic dermatitis, intradermal testing is the test of choice, and there are few reports on the use of skin prick test (SPT) in dogs. The purpose of this study was to evaluate SPT reactions in atopic dogs and a healthy control group to 11 environmental allergens. Eleven glycerinated allergens were applied on the left lateral thorax of nine atopic dogs and nine healthy dogs. The skin was pricked with a feather lancet and evaluated for the positive percutaneous reaction at 5, 10, 15, and 20 min after the application of the allergens. Data were analyzed by the Shapiro-Wilk test to test for normal distribution. Data that did not meet normality were analyzed by a one-sided Wilcoxon ranked sum test with a p-value of 0.05. Six out of 9 atopic dogs tested positive for at least one of the allergens tested. None of the dogs in the control group showed a positive reaction to the allergens included in the test. Blomia tropicalis, Dermatophagoides farine, and Dermatophagoides pteronyssinus exhibited the highest reaction rate among the group of atopic dogs. There was not a statistical difference in the histamine reaction (positive control) between both groups. In this set of dogs, the test exhibited a 100% specificity and a sensitivity of 66%. The use of skin prick-test in the detection of causative allergens of human atopic dermatitis has proved to be a sensitive and specific tool frequently used by human allergists. Due to the number of similarities in canine and human atopic dermatitis, this could be a valuable tool that needs intensive research in veterinary medicine. The published research so far correlates to the results obtained in this investigation. However, future studies evaluating the concordance between in vitro specific IgE antibody assays and SPT must be carried out simultaneously to validate the test.

Tolerance to baked and fermented cow's milk in children with IgE-mediated and non-IgE-mediated cow's milk allergy in patients under two years of age

BACKGROUND

IgE-mediated cow's milk allergy (CMA) has been shown consistent in milder heated-milk tolerant and severe heated-milk reactant groups in patients older than two years. Little is known whether fermentation of milk gives rise to similar clinical phenotypes. We aimed to determine the influence of extensively heated and fermented cow's milk on the IgE-mediated and non-IgE-mediated CMA in children younger than two years.

METHODS

Subjects followed with the diagnosis of IgE-mediated and non-IgE-mediated CMA for at least six months underwent unheated milk challenge. IgE-mediated and non-IgE-mediated groups were categorised as unheated milk-reactive and tolerant, separately. Unheated milk-reactive groups were further challenged sequentially with fermented milk (yoghurt) and baked milk, 15 days apart. Allergy evaluation with skin tests, prick-to-prick tests and atopy patch tests were performed.

RESULTS

Fifty-seven children (median age: 14 months; range: 7-24 months) underwent unheated milk challenge. Eleven of 27 children with IgE-mediated CMA and 14 of 30 children with non-IgE-mediated CMA tolerated unheated milk. Among subjects who reacted to unheated milk; 15 of 16 subjects (93%) with IgE-mediated CMA also reacted to yoghurt, whereas 11 of 16 subjects (68%) with non-IgE-mediated CMA tolerated fermented milk. Thirteen subjects (81%) of the unheated milk-reactive IgE-mediated group tolerated to heated milk. None of 16 subjects of unheated milk-reactive non-IgE-mediated group reacted to baked milk.

CONCLUSION

The majority of children under the age of two years with both IgE-mediated and non-IgE-mediated CMA tolerated baked-milk products. Yoghurt was tolerated in two thirds of unheated milk reactive patients suffering from non-IgE-mediated CMA.

Specific IgE and skin prick tests to diagnose allergy to fresh and baked cow's milk according to age: a systematic review

BACKGROUND

The diagnosis of IgE-mediated cow's milk allergy is often based on anamnesis, and on specific IgE (sIgE) levels and/or Skin Prick Tests (SPT), which have both a good sensitivity but a low specificity, often causing positive results in non-allergic subjects. Thus, oral food challenge is still the gold standard test for diagnosis, though being expensive, time-consuming and possibly at risk for severe allergic reactions.

AIM

The aim of the present study was to perform a systematic review of the studies that have so far analyzed the positive predictive values for sIgE and SPT in the diagnosis of allergy to fresh and baked cow's milk according to age, and to identify possible cut-offs that may be useful in clinical practice.

METHODS

A comprehensive search on Medline via PubMed and Scopus was performed August 2017. Studies were included if they investigated possible sIgE and/or SPT cut-off values for cow's milk allergy diagnosis in pediatric patients. The quality of the studies was evaluated according to QUADAS-2 criteria.

RESULTS

The search produced 471 results on Scopus, and 2233 on PubMed. Thirty-one papers were included in the review and grouped according to patients' age, allergen type and cooking degree of the milk used for the oral food challenge. In children < 2 years, CMA diagnosis seems to be highly likely when sIgE to CM extract are ≥ 5 KU_A/L or when SPT with commercial extract are above 6 mm or Prick by Prick (PbP) with fresh cow's milk are above 8 mm. Any cut-offs are proposed for single cow's milk proteins and for baked milk allergy in children younger than 2 years. In Children ≥ 2 years of age it is hard to define practical cut-offs for allergy to fresh and baked cow's milk. Cut-offs identified are heterogeneous.

CONCLUSIONS

None of the cut-offs proposed in the literature can be used to definitely confirm cow's milk allergy diagnosis, either to fresh pasteurized or to baked milk. However, in children < 2 years, cut-offs for specific IgE or SPT seem to be more homogeneous and may be proposed.

Cow's milk allergy: from allergens to new forms of diagnosis, therapy and prevention

The first adverse reactions to cow's milk were already described 2,000 years ago. However, it was only 50 years ago that several groups started with the analysis of cow's milk allergens. Meanwhile the spectrum of allergy eliciting proteins within cow's milk is identified and several cow's milk allergens have been characterized regarding their biochemical properties, fold and IgE binding epitopes. The diagnosis of cow's milk allergy is diverse ranging from fast and cheap in vitro assays to elaborate in vivo assays. Considerable effort was spent to improve the diagnosis from an extract-based into a component resolved concept. There is still no suitable therapy available against cow's milk allergy except avoidance. Therefore research needs to focus on the development of suitable and safe immunotherapies that do not elicit severe side effect.

Evaluation of banana hypersensitivity among a group of atopic egyptian children: relation to parental/self reports

Purpose

To evaluate the frequency of banana sensitization and allergy among a group of atopic Egyptian children in relation to parental/self reports.

Methods

This is a case-control study included 2 groups of allergic children with and without history of banana allergy, each included 40 patients. They were subjected to skin prick test (SPT) using commercial banana allergen extract and prick-prick test (PPT) using raw banana, in addition to measuring the serum banana-specific IgE. Oral banana challenge was performed in suspected cases.

Results

Banana allergy was diagnosed in 3 (7.5%) patients based on positive history of allergy on exposure to banana, positive SPT/PPT and elevated banana-specific IgE. The 3 patients had bronchial asthma with exacerbation upon banana exposure. The PPT results conform with those of SPT both in diagnosis of banana allergy and in the skin reactivity to banana. Serum banana-specific IgE was detectable in the whole studied sample with higher serum level among those without history of banana allergy (P=0.005). Oral banana challenge was negative for 20 patients with history of banana allergy and positive serum banana-specific IgE but negative SPT and PPT.

Conclusions

Self/parental reports of banana allergy is high while the actual banana allergy is uncommon. The PPT seems as reliable as SPT in diagnosis of banana allergy unlike specific IgE which reflects sensitization rather than allergy. Oral food challenge remains the most helpful tool for diagnosis of food allergy in suspected cases.

Specific allergy to Penaeus monodon (seawater shrimp) or Macrobrachium rosenbergii (freshwater shrimp) in shrimp-allergic children

BACKGROUND

Allergy to specific shrimp species has not been studied systematically by oral challenges. A comparison of allergy to different shrimp species, especially seawater or freshwater varieties treatment, would be useful in testing shrimp-allergic subjects.

OBJECTIVE

The aim of the study was to identify cases of specific allergy to seawater shrimp, Penaeus monodon (Pm), or freshwater shrimp, Macrobrachium rosenbergii (Mr), among shrimp-allergic children. Comparisons of skin tests using commercial and crude shrimp extracts plus the prick-to-prick (PTP) method were investigated.

METHODS

Sixty-eight children with a history of shrimp allergy and skin tests positive to shrimp were orally challenged to both shrimp species. Reactivity to skin prick tests using extracts of Pm (PmSPT), Mr (MrSPT), commercial shrimp (ComSPT), and PTP tests (PmPTP, MrPTP) was compared.

RESULTS

Food challenges identified specific allergy to Pm and Mr in 17.65% and 23.53% of the subjects, respectively. Positive and negative challenges to both shrimp species were found in 47.06% and 11.76% of the subjects, respectively. Correlations between the mean weal diameter (MWD) from ComSPT-PmSPT, ComSPT-PmPTP, ComSPT-MrPTP, PmSPT-PmPTP and MrSPT-MrPTP, but not ComSPT-MrSPT, were observed. The MWD from PmSPT and PmPTP were significantly larger in patients with positive than negative challenges to P. monodon (P<0.05). There was a trend that MWD from MrSPT were larger in patients with positive than negative challenges to M. rosenbergii (P=0.058). In the Pm allergy group, PmSPT with an MWD of 30 mm provided 80% predictive probability for positive challenges. PmPTP and ComSPT with an MWD of 22.5 and 20 mm provided 95% predictive probability, respectively. In the Mr allergy group, MrSPT with an MWD of 30 mm provided 95% predictive probability.

CONCLUSION

Specific allergy to Pm or Mr was confirmed by food challenges. SPT using crude extracts and the PTP test are useful tools for screening shrimp sensitization before a food challenge. The predictive probability of SPT is helpful where a food challenge is not feasible.

Potential, pitfalls, and prospects of food allergy diagnostics with recombinant allergens or synthetic sequential epitopes

This article aims to critically review developments in food allergy diagnostics with regard to the verification of specific IgE antibodies and the identification of the responsible allergens. Results of IgE-binding tests with food extracts are hampered by cross-reactive proteins, low-quality test agents, or both. Specificity can be increased by defining adequate cutoff values, whereas sensitivity can be improved by using high-quality test agents. IgE-binding tests with purified allergens enabled reliable quantification of allergen-specific IgE titers, with higher levels found in individuals with food allergy compared with individuals without food allergy. However, the overlap in individual test reactivity between allergic and nonallergic subjects complicates interpretation. Recombinant allergens and synthetic sequential epitopes enabled detection of sensitization profiles, with IgE specific to several allergens and substructures now being suggested as markers of severity, persistence, or both. However, high-power quantitative studies with larger numbers of patients are required to confirm these markers. IgE-binding tests merely indicate sensitization, whereas the final proof of clinical relevance still relies on family/case history, physical examinations, and provocation tests. Novel technologies promise superior diagnostics. Microarray technology permits simultaneous measurement of multiple IgE reactivities regarding specificity, abundance, reactivity, or interaction. Improved functional tests might enable reliable estimation of the clinical relevance of IgE sensitizations at justifiable expenses.

Prevalence of sensitization reported and objectively assessed food hypersensitivity amongst six-year-old children: a population-based study

There is a paucity of information on food hypersensitivity (FHS) in young children and there are even fewer population-based studies in this area. The aim of the study was to determine the prevalence of parentally reported FHS, and objectively diagnosed FHS amongst six-year-old children and to establish the rates of sensitization to key allergens. This population-based cohort study recruited 798 6-year-olds resident on the Isle of Wight (UK). Sensitization rates, reported rates of FHS and objectively assessed FHS was established using food challenges. A total of 94 (11.8%) 6 yr olds reported a problem with a food or food ingredient. The rate of sensitization to the pre-defined panel of food allergens was 25/700 (3.6%). Based on open food challenge and/or suggestive history and skin tests, the prevalence of FHS was 2.5% (95% CI 1.5-3.8). Based on double-blind challenges, a clinical diagnosis or suggestive history and positive skin tests, the prevalence was 1.6% (95% CI 0.9-2.7). The rates of perception of FHS are higher than the prevalence of sensitization to main food allergens and the prevalence of FHS based on food challenges. Milk, peanut and wheat were the key food allergens amongst those with positive challenges.