Diagnostic oral food challenges: procedures and biomarkers

Oral food challenge (OFC) is the gold standard for the diagnosis of food allergy. They are conducted to confirm whether an allergy to food exists (initial challenge) or to monitor for resolution of a food allergy. The history of an immediate allergic reaction, when supported by positive tests for specific IgE antibodies to the suspect food, is often sufficient to establish a diagnosis without OFC. Additionally, higher concentrations of food-specific IgE or larger allergy prick skin test wheal sizes correlate with an increased likelihood of a reaction upon ingestion. Although these food-specific IgE tests are helpful biomarkers of allergy, their limited sensitivity and specificity often necessitates the use of OFC to establish reactivity. Furthermore, the pathogenesis of non-IgE-mediated food allergy, such as food protein-induced enterocolitis (FPIES) or proctocolitis and food allergy due to mixed IgE and non-IgE mediated processes, such as atopic dermatitis or eosinophilic gastroenteropathies may not be assessable with specific IgE tests, also warranting OFCs. This review provides an overview on the technique and interpretation of OFCs, use of food-specific testing to predict whether OFC is warranted and to predict OFC outcomes. Additionally, biomarkers that correlate with OFC outcomes will be discussed, as well as future diagnostic tests promising better predictive value.