鸡蛋是儿童过敏性皮炎(AD)最常见的食物。本研究旨在确定南非AD患儿鸡蛋过敏的患病率、组份模式及筛查试验的预测值。这是在开普敦一所儿科大学医院进行的一项前瞻性观察研究。随机招募6个月到10岁的AD患儿。通过问卷调查、皮肤点刺(SPT)、免疫固相过敏原芯片(ISAC 103®)检测、对鸡蛋和卵类粘蛋白（Gal d 1）的ImmunoCAP组份测试和附加食物激发试验评估他们对鸡蛋的敏感性和过敏情况。100位参与者（59非洲黑人和41混合族群），平均年龄42月。有高达54%的鸡蛋敏感率和25%的鸡蛋过敏发病率。病史和实验室筛查试验对鸡蛋过敏发病率的估计明显过高。在诊断鸡蛋过敏中，新鲜鸡蛋白皮肤点刺试验比商用鸡蛋白提取物皮肤点刺试验更为敏感，并且其产生的ROC曲线下面积在所有的预测真正鸡蛋过敏的筛查试验中最大。在那些对鸡蛋敏感的受试者中，卵类粘蛋白组份是区分鸡蛋过敏和耐受的最佳组份。鸡蛋SPT和鸡蛋白ImmunoCAP通常用的95%阳性预测值在该人群的总的阳性预测值分别57%和74%，在黑人中预测值通常比混合人种要低。该人群中，以对鲜鸡蛋的皮肤点刺值17mm和鸡蛋白ImmunoCAP值13 kU/l作为标准判断鸡蛋过敏有最好的阳性预测值。
Egg sensitization, allergy and component patterns in African children with atopic dermatitis
Egg allergy is the most common food allergy in children with atopic dermatitis (AD). This study aimed to determine the prevalence of egg allergy, component patterns and predictive values of screening tests in egg allergy in South African children with AD.
This was a prospective, observational study in a paediatric university hospital in Cape Town. Children with AD, aged 6 months to 10 years, were recruited randomly. They were assessed for sensitization and allergy to egg by questionnaire, skin prick tests (SPT), Immuno Solid Phase Allergen Chip (ISAC 103®) test, ImmunoCAP component tests to egg and ovomucoid (Gal d 1) and incremental food challenges.
Hundred participants (59 Black Africans and 41 of mixed ethnicity) were enrolled, median age 42 months. There was a high rate of egg sensitization of 54% and prevalence of confirmed egg allergy of 25%. History and screening laboratory tests overestimated egg allergy significantly. SPT to fresh egg white was significantly more sensitive in diagnosing egg allergy than SPT to the commercial egg white extract and produced the highest area under the receiver operator characteristics curve of all the screening tests in predicting true egg allergy. In those participants sensitized to egg, the component ovomucoid was best at differentiating true egg allergy from tolerance. Commonly used 95% positive predictive values (PPVs) for SPT to egg and ImmunoCAP egg white produced low PPV of 57% and 74%, respectively, in this population overall, with generally poorer predictive values amongst the Black Africans than the mixed ethnicity participants. A SPT to fresh egg of 17 mm and ImmunoCAP egg white of 13 kU/l produced the best PPV for egg allergy in this population.
The prevalence of egg allergy is high in African children with AD, but history of egg allergy and sensitization to egg significantly overestimate the true egg allergy rate. SPT to fresh egg white was more sensitive than that to commercial egg white extract; hence, fresh egg white should be recommended in an egg allergy screening panel. The component ovomucoid was useful for differentiating allergy from tolerance in egg‐sensitized participants. Population‐specific 95% PPV for egg allergy tests may need to be established in developing world populations.
Claudia L. Gray Michael E. Levin George du ToitKing's Health Partners, MRM & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, UKDepartment of Paediatric Allergy, Guy's and St Thomas' NHS Foundation Trust, London, UK