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Peanut allergy is a leading cause of fatal anaphylaxis. Labelled intracellular Diamine Oxidase (DAO) has been used to measure basophil histamine release at a single cell level. We hypothesized that the intracellular DAO assay can be used a functional diagnostic tool for identifying peanut allergic patients, and monitor basophil response following an oral peanut challenge, which may improve our ability to predict those at risk of anaphylaxis.
Methods:
Basophil activation and histamine release was measured in peanut allergic patients (n=10), peanut sensitized (n=4) undergoing an oral food challenge and non-atopic controls (n=10) by expression of CD63 and intracellular DAO by flow cytometry. Additionally, basophil responses were measured before, during and after in vivo peanut challenge.
Results:
CD63+CRTh2+ basophils were significantly increased and DAO+CD63-CRTh2+ basophils were decreased in peanut allergic compared to non-allergics (P<0.001, P<0.001). A strong correlation was observed between basophil activation and degranulation (r=-0.9140, P<0.0001). There was an increasing trend in basophil activation and degranulation during in vivo active peanut challenge. ROC analysis revealed the assay cut off for DAO assay was 93.9%, with clinical sensitivity 92.9% and specificity of 90%, with the likelihood ratio of 9.29. For CD63, this was 2.7%, with clinical sensitivity and specificity of 85.7% and 90% respectively, and likelihood ratio of 8.57.
Conclusions:
In this pilot study, we show for the first time that the DAO assay used in conjunction with CD63 may potentially be utilised to distinguish peanut allergic from non allergic individuals.