The Clinical Impact of the Basophil Activation Test to Diagnose Food Allergy

The BAT Impact study is a prospective multicentre study in the UK using a biomarker-led study design to compare the incidence of adverse events (defined as allergic reactions during oral food challenges) in a randomized-controlled trial. Patients will either follow the standard-of-care (i.e. an oral food challenge in case of equivocal SPT/sIgE) or follow a basophil activation test (BAT)/mast cell activation test (MAT)-based strategy, i.e. patients with a positive BAT or MAT are dispensed of an oral food challenge (OFC) and patients with a negative BAT/MAT undergo an OFC.

Children aged 6 months to 15 years requiring an oral food challenge to one of the study foods (milk, egg, peanut, sesame or cashew nut) will be invited to participate in the study.

Eleven centres across the UK will be recruiting participants and perforning clinical procedures, such as skin prick testing and oral food challenges (OFC), as per standard clinical care.

Participants will be randomised 4:5 to either have the standard-of-care, i.e. oral food challenge to the suspected food, or take BAT (MAT if BAT inconclusive) into account to decide whether or not OFC will be required: if BAT/MAT is positive, food allergy will be confirmed without doing OFC; if BAT/MAT is negative, participants in the biomarker arm will undergo OFC.

The primary outcome is the proportion of positive OFC in the biomarker arm compared with the standard-of-care arm.

Secondary outcomes are: number of OFC, quality of life, anxiety and costs associated with the diagnostic work-up.

Eligibility Criteria:
Inclusion Criteria:

* Children and young people aged 6 months to 15 years
* Suspected allergy to one of the study foods (peanut, cow's milk, egg, cashew, sesame) - defined as:

  * history of clinical reaction or
  * evidence of IgE sensitisation (SPT\>0mm and/or specific IgE\>=0.10 KU/L) to the respective food or
  * reassessment for possible resolution of allergy to the specific food following previous diagnosis of food allergy
* Need for an oral food challengeOFC to the study food
* Oral food challengeOFC to reach amount of food protein in a typical portion size for child's age
* Consent from adults with parental responsibility and assent from children and young people in an age appropriate form.

Exclusion Criteria:

* Clinically significant chronic illness other than atopic diseases;
* Previous history of severe life-threatening reaction to the suspected food with documented decrease in oxygen saturation (\<90%), hypotension (≥20% reduction in systolic blood pressure) and/or admission to intensive care;
* Unwillingness to comply with study procedures, namely to undergo a diagnostic food challenge;
* Contra-indication for diagnostic food challenge, namely:

  * Uncontrolled atopic diseases (e.g. eczema, asthma, rhinitis);
  * Chronic medical conditions that pose significant risk in the event of anaphylaxis or treatment of anaphylaxis (e.g. cardiac disease, severe lung disease, pregnancy, mastocytosis);
  * Inability to discontinue medications that might interfere with assessment or safety (e.g. antihistamines, β-agonists, β-blockers, NSAIDs, ACE inhibitor, antacids);
  * Recent (within 7-14 days) treatment with systemic steroids or prolonged high-dose systemic steroids or immunosuppressants;
* Undergoing treatment with omalizumab, food or inhalant allergen immunotherapy or other systemic immunomodulatory treatment;
* Inability to stop anti-histamines prior to SPT or OFC.