Basophil Activation Test to Diagnose Food Allergy

• Oral food challenge (Diagnostic test), also known as Basophil activation test, Skin prick test, Specific IgE test: Patients with suspected food allergy will undergo clinical and dietary assessments and oral food challenge. Different allergy tests will be performed, including skin prick test, specific IgE test and basophil activation test, and its diagnostic utility will be determined against the clinical gold-standard.

Primary outcomes

• Diagnostic accuracy of the basophil activation test (for each individual food allergy) [3 years]: Accuracy of %CD63+ basophils

Secondary outcomes

• Diagnostic accuracy of SPT, specific IgE to extracts and to single allergens [3 years]: Accuracy of weal diameter or level of IgE
• Association between BAT and severity of symptoms during challenges [3 years]: Correlation between %CD63+ basophils and severity grade
• Association between BAT and threshold of reactivity during challenges [3 years]: Correlation between CD-sens and cumulative threshold dose

Sex: All, ages: 6 Months to 16 Years

Inclusion Criteria:

1. Children ≥6 months and <16 years old;
2. Suspected IgE-mediated food allergy defined by:

   * History of an immediate-type allergic reaction to a specific food or
   * No history of consumption of the specific food or
   * IgE sensitisation documented by skin prick test (≥1 mm) or serum specific IgE (≥0.10 KU/L);
3. Avoidance of the specific food for at least 2 days prior to blood collection for BAT and specific IgE and prior to the challenge;
4. Informed consent obtained from parent or guardian and assent obtained from the child.

Exclusion Criteria:

1. Clinically significant chronic illness other than atopic diseases;
2. 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;
3. Unwillingness to comply with study procedures, namely to undergo a diagnostic food challenge;
4. 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;
5. Undergoing treatment with omalizumab, food allergen immunotherapy or other systemic immunomodulatory treatment;
6. Inability to stop anti-histamines prior to SPT.

• Results publication: Bartha I, Boyd H, Foong RX, Krawiec M, Marques-Mejias A, Marshall HF, Radulovic S, Harrison F, Antoneria G, Jama Z, Kwok M, Pietraszewicz E, Eghleilib M, Ricci C, Marrs T, Lack G, Du Toit G, Santos AF. The Basophil Activation Test Is the Most Accurate Test in Predicting Allergic Reactions to Baked and Fresh Cow's Milk During Oral Food Challenges. Allergy. 2025 Oct;80(10):2861-2873. doi: 10.1111/all.16675. Epub 2025 Aug 13. PMID 40808324
• Results publication: Marques-Mejias A, Radulovic S, Foong RX, Bartha I, Krawiec M, Kwok M, Jama Z, Harrison F, Ricci C, Lack G, Du Toit G, Santos AF. Partial Egg Consumption Modifies the Diagnostic Performance of Allergy Tests to Predict Outcome of Double-Blind Placebo-Controlled Food Challenges to Egg. J Allergy Clin Immunol Pract. 2024 Mar;12(3):660-669.e5. doi: 10.1016/j.jaip.2023.12.036. Epub 2023 Dec 27. PMID 38157981

• Alexandra Santos, MD PhD, Principal investigator, King's College London