Published Online: January, 2015
Peanut allergic patients often react to small amounts of the allergens with symptoms that can be life-threatening. Various factors have been described as conferring a greater risk of severe reactions to peanut in allergic patients but so far no objective marker of how severe accidental reactions to peanut may be or of the dose to which an individual patient is likely to react have been identified. Currently, the method of choice to determine the severity and the threshold dose at which patients react is oral food challenges (OFC), which consist of giving the culprit food in hospital, to patients known to be allergic. The management of peanut allergy relies on allergen avoidance and the use of an epinephrine auto-injector as rescue treatment in the severe cases. A test that could identify the patients at risk of severe reactions and/or at risk of reacting to trace amounts of the allergens could significantly improve the care for patients with peanut allergy.
In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), Santos and colleagues assessed the utility of a new diagnostic test, the basophil activation test (BAT), in identifying patients at risk of severe allergic reactions to peanut and patients at risk of reacting to small amounts of the allergens. Basophils are blood cells involved in peanut allergic reactions, including anaphylaxis. The BAT is a flow cytometry-based test where the reaction of basophils to peanut allergens is assessed in a test tube and can be seen as an in vitro surrogate of OFC. The authors performed BAT in 52 children who reacted to peanut on OFC on the same day of the OFC. They determined the severity and the threshold of allergic reactions to peanut during OFC and related these to the results of the BAT and to the results of other allergy tests that are routinely used in the clinic.
BAT showed to reflect the severity and the threshold of allergic reactions to peanut during OFCs. Peanut allergic patients in the study reacted to different doses of peanut allergens (57% reacted to 0.1g or less of peanut protein) with symptoms that ranged from mild tingling in the mouth to anaphylaxis (41% of cases had severe reactions and 18% required injectable epinephrine during the OFCs). The more basophils that are activated in response to peanut in the BAT the more severe the symptoms during the OFCs. The dose of peanut protein that the basophils reacted in the BAT was associated with the dose of peanut protein at which the patients reacted during the OFCs. BAT was more informative in predicting the severity and the threshold of allergic reactions to peanut than skin prick or specific IgE testing or the combination of BAT with these tests. To better translate their findings to clinical practice, the authors identified the results of BAT above which the risk of severe reactions would increase by 3-fold and the results of BAT above which the risk of reacting to trace amounts of peanut would increase by 2-fold.
Santos and colleagues concluded that BAT to peanut can estimate the severity and the threshold of allergic reactions to peanut during OFCs and identify high-risk patients who require special attention. The additional information provided by BAT should be interpreted in light of the previous clinical history and the presence of other risk factors for each individual patient. Following further studies, BAT may improve the care for patients with peanut and possibly other food allergies in the future.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.