Reproducibility of food challenge to cow’s milk: Systematic review with individual participant data meta-analysis

BACKGROUND: Cow's milk (CM) is an increasingly common cause of severe allergic reactions, but there is uncertainty with respect to severity of reactions at low-level CM exposure, as well as the reproducibility of reaction thresholds. OBJECTIVE: We undertook an individual participant data (IPD) meta-analysis of studies reporting double-blind, placebo-controlled food challenges in CM to determine the rate of anaphylaxis to low-level exposures and the reproducibility of reaction thresholds. METHODS: We performed a systematic review and IPD meta-analysis of studies reporting relevant data. Authors were contacted to provide additional data and/or clarification as needed. Risk of bias was assessed using the National Institute for Clinical Excellence methodologic checklists. Then 110 individuals underwent repeat double-blind, placebo-controlled food challenges; the intraindividual variation in reaction threshold was limited to a ½-log change in 80% (95% CI, 65-89) of participants. Two individuals initially tolerated 5 mg CM protein but then reacted to this dose at a subsequent challenge, although neither had anaphylaxis. CONCLUSIONS: dose, respectively, in the broader CM-allergic population. Most of these anaphylactic reactions would be mild and respond to a single dose of epinephrine.