Basophil Activation Test (BAT) Sensitivity in Child Food Allergy
Condition: Allergy to Egg; Allergy to Peanut
MeSH terms: Hypersensitivity; Food Hypersensitivity; Peanut Hypersensitivity
Study type: Interventional
Phase: Phase 4

Summary: 
      Child food allergy represent 6 to 8% of child in industrialised country. Within this allergy,
      peanuts and egg allergy are one of the most common.

      Actually when there is a suspicion of food allergy, the OPT is the gold standard for the
      diagnosis. During the OPT we give increasing doses of the allergen to the patient and
      evaluate threshold causing a clinical reaction. This test is associated with a risk of strong
      allergic reaction and need a medical supervision.

      Standard allergy test, like skin test or specific IgE test, can't be use for the diagnosis of
      these allergy. Some publications demonstrate that these tests lack sensibility and
      specificity for child food allergy diagnosis.

      New tests have to be develop to diagnosis child food allergy without risks. The BAT is a
      cellular test able to evaluate the basophiles activation by specific allergen in vitro. This
      test allow us to evaluate more physiologically the sensitization of patients to an allergen.
      It is already used in drug allergy and it has been evaluated in infant milk allergy in an
      other clinical trial.

      In this study we want to evaluate the sensitivity of BAT to the diagnosis of child food
      allergy compare to the gold standard test OPT. We will evaluate the BAT on 140 children with
      food allergy and compare this results with the OPT at the same time. If the BAT results can
      predict the sensitivity of children to food allergen, it could limit the use of the OPT and
      reduce the risk of this test.
    

Detailed description: 
      Child food allergy represent 6 to 8% of child in industrialised country. One third of these
      child will develop severe reactions and one third will experience multiple allergy. In
      France, there is few epidemiologic data but in 2005 F. Rancé evaluated the prevalence of
      these allergy to 6.7% of school child. Within the food allergen, peanut, egg and milk are the
      most common.

      Currently, there is two diagnostic possibilities:

        -  A strong allergic reaction with identified allergens and specific IgE positive, making
           it highly probable diagnosis.

        -  A moderate allergic reaction with only suspicion on the allergen, without definitive
           diagnosis.

      When there is a suspected allergy, the gold standard to the diagnosis is the OPT. This test
      consist of the gradual ingestion of the suspected food allergen to evaluate the threshold
      causing a clinical reaction. The OPT must be performed under medical supervision in a
      hospital due to the risk of severe allergic reaction.

      The OPT is the gold standard in allergy diagnosis. The other tests (prick test, IgE specific
      measure…) are not sensitive enough. Furthermore, the level of IgE specific was not related to
      the risk to develop clinical reaction to the food allergen. Some studies have try to combine
      skin tests with the result of IgE specific measure but the sensitivity did not improve
      enough.

      New tests have to be develop to diagnosis child food allergy without risks. The BAT is a
      cellular test able to evaluate, in blood, the basophiles activation by specific allergen in
      vitro. This test measure by flow cytométrie the expression of activation molecule (CD63) on
      basophiles (CCR3+) after incubation with the allergen. If the patient is sensitize to the
      allergen, the percentage of active basophiles will be higher than in non sensitize people.
      This test allow us to evaluate more physiologically the sensitization of patients to an
      allergen. This test has already been tested for drug allergy and milk allergy in child. This
      clinical trial demonstrated that in mill allergy, the BAT had a good sensitivity (91% and
      sensibility (96%). Furthermore, this study could determined the threshold of the BAT in child
      food allergy (6% of activated basophiles).

      In light of these results, we want to evaluate the advantage of BAT compare to OPT in child
      with allergy to egg or peanut.

      During this study, we will perform BAT on a blood sample from child suspected of food allergy
      (egg or peanut) before OPT and we will compare its results with the OPT results. The primary
      objective of this study is to evaluate the BAT interest to predict the results of OPT by
      analysing the sensibility, specificity, positive predictive value, negative predictive value
      of BAT.

      If these study demonstrate that BAT can predict OPT results for child food allergy, we will
      be able to reduce the number of OPT for these patients and reduce the risk of anaphylactic
      shock during OPT.
    

Intervention name(s): Basophil Activation Test
Intervention type(s): Biological
Intervention description(s): blood sample for Basophil Activation Test
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: diagnosis of allergy; Basophil Activation Test