A Comparison of Double-Blind, Placebo-Controlled Food Challenge and Open Food Challenge

Open food challenges are commonly performed in clinical practice when evaluating adverse food reactions. The goal standard for confirming IgE-mediated food allergies is the double-blind, placebo-controlled food challenge (DBPCFC). These are labor intensive and time-consuming procedures that are not practical in most clinical practice settings. This study assessed the validity of open challenges by comparing severity of symptoms and threshold values (cumulative dose of food allergen eliciting a clinical reaction) in children and adults with peanut allergy, challenged in an open and double-blind placebo-controlled protocol.Patients with a positive peanut challenge at Allergy Centre at Odense University Hospital, Denmark between September 2001 and February 2022. Negative or inconclusive challenges were excluded. Children under the age of 6 were excluded, as only open food challenges were performed on this age group at this center.A retrospective review of all positive peanut challenges conducted at a university-based allergy clinic over a 20-year period was performed. Positive challenges were defined by strict objective signs. Severity of symptoms was graded using Sampson’s severity score. Distribution models of threshold values were calculated using log-normal interval-censored survival analysis. Additional analysis included direct comparison of patients who underwent both an open challenge and a DBPCFC. The study reported the number of placebo reactions.There were 1381 food challenges to peanut performed from 2001 to 2022. There were 318 positive open challenges and 86 positive DBPCFC to peanut. Fifteen patients had both types of challenges conducted. There was no significant difference in severity of symptoms, nor threshold values, when comparing the 2 challenge types. Moderate symptoms were experienced by 78% of patients undergoing open challenges versus 77% of patients during DBPCFC. The median eliciting dose was 248.7 mg peanut protein for open food challenges versus 219.2 mg peanut protein for DBPC.Open food challenges, when performed using strict objective criteria by trained staff, are appropriate substitutes for the gold standard evaluation, double-blind placebo-controlled challenges.Open food challenges are an important procedure that is essential in evaluating suspected food allergies when either clinical history or food specific allergy testing is inconclusive. This study adds additional data confirming that open food challenges are an appropriate substitute for the more labor-intensive DBPCFC. Threshold peanut values were also presented and showed in this population and only a small subset 1% to 2% of patients reacted at 10 mg. It would be of great value if could determine these threshold doses when considering oral immunotherapy or treatment with omalizumab for those patients at greatest risk for cross contact reactions.