Improvement of the Specificity of the Indirect BAT for the Diagnosis of Peanut Allergy; the BA(Blocking Antibodies)-BAT

Abstract

These false-positive outcomes can be a consequence of IgE binding to an epitope in the food protein used in these tests that may be inactivated after consumption due to food processing or digestion. Alternatively, the BAT protocol can be less sensitive to interference of inhibiting factors such as allergen specific IgG4 and IgA produced during tolerance development due to e.g. consumption of trace amounts of allergen. However, the influence of inhibiting factors can be detected when allergens are pre-incubated with serum, allowing IgG/IgA binding to allergens, before addition to basophils, as shown by the fact that a decrease in basophil sensitivity to Ara h2 predicted sustained unresponsiveness after peanut oral immunotherapy [4]. In our recent study on the indirect BAT for the diagnosis of peanut allergy we observed a few false-positive BAT outcomes [3]. We hypothesized that these false-positive BAT outcomes might among others be due to inhibiting factors, like IgG4 and IgA, produced during natural tolerance development which effect on basophil activation can’t be adequately detected in the regular BAT protocol. Therefore, we re-analysed with a modified indirect BAT protocol (called “BA(blocking antibodies)-BAT”) the serum samples (n=3) from our indirect BAT peanut study with a false-positive BAT Ara h2 or Ara h6 outcome.