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.

Tree nut allergy and anxiety related factors modulate food consumption behaviour in peanut-allergic patients: Results of the MIRABEL survey.

BACKGROUND: In the absence of specific data on food consumption of allergic consumers, general population surveys are used for risk assessment. Most of allergy risk assessment's experts advise that an understanding of the food consumption habits of people with food allergies is crucial for correctly estimate the risk. OBJECTIVE: This study aims to detail the food consumption of patients with peanut allergy including products with precautionary allergen labelling (PAL) and to identify the factors influencing their consumption behaviour. METHODS: The MIRABEL study is a multi-center survey of peanut-allergic patients from France, Belgium and Luxemburg. It includes data on medical, socio-demographic, and consumption of different food categories, including products with PAL. Anxiety score and allergy severity level variables were constructed and studied as potential consumption determinants. To study the association of modulator variables with food consumption, a logistic regression model was built to test the association with food category and ingredient choice. RESULTS: 443 of the 785 patients from MIRABEL survey were included in the consumption study. Tree nut allergy, knowledge of threshold dose, label reading and anxiety score significantly influenced the consumption of products which may contain unintended traces of peanut. The direction of influence depended on food categories and ingredient choices. Diet advice by allergists, severity of the allergy and threshold dose determined by oral food challenge did not significantly impact consumption. CONCLUSIONS: and clinical relevance: It showed, for the first time, that consumption of food products by peanut-allergic patients, including those with PAL, is modulated by factors related to anxiety such as label reading and knowledge of threshold and concomitant tree nut allergy. Knowledge of peanut-allergic food behaviours will make it possible to improve risk assessment and help allergists and risk managers to make diet advices.

A statistical model to detect asymptomatic infectious individuals with an application in the Phytophthora alni-induced alder decline.

In some diseases-in particular, tree root infection-stages of infection and inoculum production level and timing are not readily observable because of uncertainty or time lags in symptom appearance. Here, we pose a criterion, based on relative hazard of disease symptoms, to discriminate between healthy and asymptomatic infected individuals. We design a statistical procedure to estimate the criterion for a 6-year survey of alder decline along a northeastern French river. Individual tree symptom hazard was modeled with Cox's regression model, taking estimation of local infection pressure as a risk factor. From an inoculum production experiment, we thereafter assessed the inoculum production level of target trees, including symptomatic and asymptomatic trees ranked according to their symptoms hazard. Using receiver operating characteristic methods, we first evaluated the criterion performance and determined the discrimination threshold to sort out asymptomatic individuals into healthy and infected. Then, we highlighted the fact that the infected asymptomatic trees were among the major inoculum producers whereas severely declining and dead trees were found to be poor inoculum sources.