Clinical implications of food allergen thresholds

Targeted proteomics for rapid and robust peanut allergen quantification

This study improves LC-MS-based trace level peanut allergen quantification in processed food by refining method robustness, total analysis time and method sensitivity. Extraction buffer (six compared) and peptide choice were optimised and found to profoundly affect method robustness. A rapid extraction and in-solution digestion method was developed omitting subsequent reduction, alkylation and sample clean-up steps effectively reducing total analysis time from the previously reported ∼5.5-20 h to ∼2.5 h. For the three best performing peptides, accurate quantification (CVs < 15%) with matrix-matched calibration curves (R² = 0.99-0.97) was achieved for peanut muffin and ice-cream with excellent linearity (0.25-1000 mg kg^-1). The best performing peptide enabled excellent recovery rates in ice-cream (106.0 ± 15.1%) and peanut muffin (72.7 ± 13.4%). Sensitivity (LOD = 0.25-0.5 mg kg^-1; LOQ = 0.5-1.0 mg kg^-1) was 2- to 20-fold improved compared to previous methods depending on the peptide. These methodological improvements contribute to robust peanut detection in food and can be translated to additional food-borne allergens.

Adaptation, Translation and Validation of the Food Allergy Quality of Life Questionnaire-Parent Form (FAQLQ-PF): The Malay Version

Food allergy has a significant impact on the quality of life (QoL) of children and can be measured using The Food Allergy Quality of Life Questionnaire-Parent Form (FAQLQ-PF). This study aimed to adapt, translate the FAQLQ-PF into Malay and determine the validity and reliability of the translated version. This cross-sectional questionnaire validation study was conducted among parents of children (0 to 12 years old) with food allergies across five sites in Selangor and Kuala Lumpur, Malaysia. The FAQLQ-PF-Malay underwent cross-cultural adaptation, translation, validation (content, face and construct) and reliability assessment. Exploratory factor analysis, internal consistency and test-retest reliability analyses were used to examine its construct validity and reliability. Out of 150 children, the majority were between the age of 7 to 12 years old (41%) and were female (81%). Three subscales were identified, which were: (i) social and dietary implication, (ii) food anxiety and (iii) emotional and physical impact. Four items were eliminated because of weak factor loadings. The Cronbach’s alpha for each subscale ranged from 0.88 to 0.94, with an overall Cronbach’s alpha of 0.95. The intra-class correlation coefficient ranged from 0.54 (95% CI: 0.10–0.77) to 0.97 (95% CI: 0.90–0.99). The 26-item FAQLQ-PF-Malay retained the three-factor structure of the original FAQLQ-PF. The FAQLQ-PF-Malay is a valid and reliable tool to assess the QoL of Malaysian children with food allergies.

Survey of Commercial Food Products for Detection of Walnut (Juglans regia) by Two ELISA Methods and Real Time PCR

Labeling of food allergens in accordance with legal regulations is important to protect the health of allergic consumers. The requirements for detecting allergens in foods involve adequate specificity and sensitivity to identify very small amounts of the target allergens in complex food matrices and processed foods. In this work, one hundred commercial samples were analyzed for walnut detection using three different methods: a sandwich enzyme-linked immunosorbent assay (ELISA) kit based on polyclonal antibodies, a direct ELISA using a recombinant multimeric scFv, and a real time PCR. The most sensitive method was real time PCR followed by sandwich ELISA kit and multimeric scFv ELISA. There was agreement between the three methods for walnut detection in commercial products, except for some heat-treated samples or those that contained pecan. The walnut ELISA kit was less affected by sample processing than was the multimeric scFv ELISA, but there was cross-reactivity with pecan, producing some false positives that must be confirmed by real time PCR. According to the results obtained, 7.0 to 12.6% of samples (depending on the analytical method) contained walnut but did not declare it, confirming there is a risk for allergic consumers. Moreover, there was one sample (3.7%) labelled as containing walnut but that tested negative for this tree nut. Genetic and immunoenzymatic techniques offer complementary approaches to develop a reliable verification for walnut allergen labeling.

Can my child with IgE-mediated peanut allergy introduce foods labeled with "may contain traces"?

Peanut IgE-mediated food allergy is one of the most common food allergies in children with a prevalence that has increased in the past decades in Westernized countries. Peanut allergies can trigger severe reactions and usually persist over time. Peanut-allergic children and their families are often confronted to processed foods with precautionary allergen labeling (PAL) such as "may contain traces of peanuts," which are frequently used by the food industry. Patients are generally confused as to whether eating such foods entails a risk of allergic reaction, which can ultimately lead to dietary restrictions and decreased quality of life. Thus, guidance toward eviction of foods with PALs such as "may contain traces of peanuts" is a recurring problem that peanut-allergic patients address during pediatric allergy consultations with varying attitudes among allergists. Many studies have evaluated peanut contamination in foods with PALs, with generally less than 10% of foods containing detectable levels of peanuts, albeit heterogeneous amounts, with in rare occasions levels that could trigger allergic reactions in certain patients. The risk of reacting to foods with traces varies significantly with threshold, with patients with the lowest reaction thresholds at highest risk, and a dramatic reduction of risk as threshold increases. Thus, risk stratification based on individual reaction threshold may help stratify patients' risk of reacting to foods with PAL. In clinical practice, a single-dose 30 mg peanut protein oral food challenge may be an option to stratify peanut-allergic patients' risk when introducing foods with PAL, as illustrated by three clinical cases.

Gender, prick test size and rAra h 2 sIgE level may predict the eliciting dose in patients with peanut allergy: Evidence from the Mirabel survey

BACKGROUND

Peanut allergy management is based on active avoidance and access to emergency treatment including self-injectable adrenaline. Knowing the dose at which a patient is likely to react is crucial for risk assessment and could significantly improve management by integrating a personalized approach.

OBJECTIVE

To develop a threshold dose distribution curve model from routinely collected data.

METHODS

The MIRABEL survey is an observational study of 785 patients with peanut allergy/sensitization conducted in France, Belgium and Luxemburg. The current analysis included the 238 participants for whom medical and oral food challenge data were available. Several statistical models (Kaplan-Meier, Cox model, Weibull and Lognormal with predictive factors, basic Weibull and Lognormal) were compared to select the best model and predictive factor combination associated with the threshold doses. Inferences were made with a Bayesian approach.

RESULTS

Patients were mainly children (mean age: 9 years [IQR: 6-11]; 87% < 16 years) and males (62%). Median Ara h2 s IgE was of 8kUA/L [IQR: 1-55] and median skin prick test size of 10 mm [IQR: 7-13]. OFC was positive in 204 patients (86%). The median threshold dose was of 67 mg of peanut protein [IQR: 16-244]. The dose at which 1% of the patients are likely to react with objective symptoms was 0.26 [0.03; 2.24] mg of peanut protein. Gender, size of the skin prick test (SPT) and Ara h 2 specific IgE level had a significant impact on the threshold dose distribution curve. The Cox model was the most effective to predict threshold doses with this combination of factors. Girls react to lower doses than boys with a beta coefficient associated to the risk and a 95% credible interval of 0.44 [0.04; 0.77]. The higher the size of the SPT and the Ara h 2 specific IgE level are, the higher the risk of reacting to a small amount of peanut, with beta coefficients associated to the risk and 95% credible intervals of 0.05 [0.02; 0.08] and 0.01 [0.01; 0.02], respectively.

CONCLUSION AND CLINICAL RELEVANCE

According to the model, routinely collected data could be used to estimate the threshold dose. The consequences could be the identification of high-risk patients who are susceptible to react to small amounts of peanut and a personalized management of peanut allergy integrating the risk of allergic reaction. Limitations of this study are that assessors of OFC outcome were aware of SPT and Arah2 results, and a further validation study is required to confirm the predictive value of these parameters.