Supplementary Material for: Early Introduction of Egg and the Development of Egg Allergy in Children: A Systematic Review and Meta-Analysis

Background: The timing of the introduction of egg to an infant’s diet is of current interest, as new evidence raises questions regarding the benefit of delaying egg introduction. The objective of this study was to systematically review the existing literature regarding the effect of the early introduction of egg on the development of egg allergy. Methods: Literature searches were conducted in MEDLINE, EMBASE, and CENTRAL, and trial protocols were searched in Meta Register and OpenGREY. Only randomized controlled trials (RCTs) comparing early (between 3 and 6 months of age) egg introduction to no early introduction were included. The primary outcome was the development of egg allergy. Results: Of the 416 articles identified and screened, 6 RCTs met the eligibility criteria for data extraction. Allergic outcomes were evaluated in a total of 3,032 participants. A low to moderate level of evidence showed a benefit of the early introduction of egg (relative risk, RR 0.60, 95% CI 0.44–0.82, p = 0.002, mild heterogeneity, I2 = 23%). The absolute risk reduction for a population with an incidence of egg allergy of 9.3% was 37 fewer cases (95% CI 17–52) per 1,000 people. Consumption of < 4,000 mg/week of egg protein had a greater preventive effect than a higher dose. Conclusion: This systematic review and meta-analysis showed an association between the early introduction of egg and a lower risk of egg allergy. Furthermore, the nature and dose of egg protein exposure may play a role. These findings should be addressed in the context of primary studies.

研究背景：婴儿辅食中鸡蛋引入的时机目前广受关注，因最新研究证据对延迟引入鸡蛋的获益提出了质疑。本研究的目的为系统综述现有文献，探讨早期引入鸡蛋对鸡蛋过敏发生风险的影响。
研究方法：本研究于MEDLINE数据库、EMBASE数据库及CENTRAL数据库（Cochrane对照试验中心注册库）中开展文献检索，并在Meta Register与OpenGREY中检索试验方案。仅纳入对比早期（3~6月龄）引入鸡蛋与未早期引入鸡蛋的随机对照试验（Randomized Controlled Trials, RCTs）。本研究的主要结局指标为鸡蛋过敏的发生情况。
研究结果：本研究共检索筛选出416篇文献，其中6项RCT符合数据提取的纳入标准。共计3032名受试者的过敏结局被纳入评估。低至中等质量的证据显示，早期引入鸡蛋可带来获益（相对风险RR=0.60，95%置信区间CI：0.44~0.82，p=0.002，轻度异质性I²=23%）。在鸡蛋过敏发病率为9.3%的人群中，绝对风险降低值为每1000人中减少37例发病（95%CI：17~52）。每周摄入鸡蛋蛋白<4000mg时，其预防效果优于更高剂量的摄入。
研究结论：本项系统综述与Meta分析显示，早期引入鸡蛋与更低的鸡蛋过敏风险存在关联。此外，鸡蛋蛋白暴露的性质与剂量或可发挥调控作用。上述研究结论需结合原始研究开展进一步探讨。