PURPOSE OF THE STUDY.
Food challenge remains the gold standard for diagnosing food allergy. Developing alternative tests with improved ability to predict outcomes of food challenges has been elusive. Determining the sensitization to individual proteins, known as component-resolved diagnosis (CRD), has improved models predicting outcomes of food challenges to peanut (Ara h 2–specific IgE) and hazelnut (Cor a 14–specific IgE). The ratio of whole allergen–specific IgE to total IgE has also been investigated for predicting food challenge outcomes. This study aim was to see if the ratio of specific-component IgE to total IgE can improve the prediction of food challenge outcomes.
Children referred to 9 pediatric allergy clinics across Germany for a first evaluation of peanut allergy, hazelnut allergy, or both were eligible. Children included were those who were sensitized to peanut or hazelnut but had no history of exposure or those who had a recent immediate food reaction wherein peanut or hazelnut was the suspected causative agent.
Blood samples were collected from participants. In suspected peanut allergy cases, specific-IgE levels against whole peanut and 4 peanut proteins (Ara h 1, Ara h 2, Ara h 3, and Ara h 8) were measured, and for suspected hazelnut allergy cases, IgE levels against whole hazelnut and 4 hazelnut proteins (Cor a 1, Cor a 8, Cor a 9, and Cor a 14) were measured. Levels were determined by using the ImmunoCAP-FEIA method. Food challenges were conducted in all participants to diagnose food allergy. Ratios of specific to total IgE were compared with raw IgE levels in terms of discrimination and prediction.
Forty-three percent of 207 children with suspected peanut allergy and 31% of 142 children with suspected hazelnut allergy were confirmed as having food allergy by a positive food challenge. There was not a significant difference between the performance measures for Ara h 2–specific IgE versus the ratio of Ara h 2–specific to total IgE (area under the curve 0.93 vs 0.92). There was also no significant difference between the performance measures for Cor a 14–specific IgE versus the ratio of Cor a 14–specific to total IgE (area under the curve 0.89 vs 0.87). The probability of positive peanut challenge with an Ara h 2–specific IgE of 0.35 kU/L was 16% when the total IgE level was >500 kU/L, compared with 48% for IgE levels of 100 to 500 kU/L and 51% for IgE levels of <100 kU/L. At a Cor a 14–specific IgE level of 0.35 kU/L, a positive food challenge was seen 7% of the time with total IgE being >500 kU/L, compared with 32% with total IgE of 100 to 500 and 34% with total IgE being <100.
Using a ratio of component-specific IgE to total IgE for peanut and hazelnut did not improve performance in predicting food allergy compared with using the specific-component levels alone. Higher total IgE levels might indicate lower probabilities of reaction at a given component-specific IgE level.
Food challenge remains the gold standard for diagnosing food allergy. A marker that would alleviate the need for time-consuming and risky food challenges has yet to be found. CRD has allowed some patients to proceed with food challenges deemed to be lower risk. At this time, we still rely on our clinical judgment based on detailed clinical history, specific allergic sensitivity, and comorbid conditions when determining the risk-to-benefit profile, allowing patients to make an informed decision to pursue a food challenge.
- Copyright © 2017 by the American Academy of Pediatrics