Prevalence patterns of allergen sensitization by region, gender, age, and season among patients with allergic symptoms in mainland China: A four‐year multicenter study

Abstract

The proportion of the population with allergic diseases has increased rapidly in recent decades.1, 2 In addition to affecting the quality of life, a significant economic burden of these diseases was transferred to society and the national health care system.1 China is a large country with a rapidly developing economy, wide geography, and diverse climate and lifestyles, which may lead to significantly regional differences in the distribution of allergens. Although a series of studies have explored the prevalence of allergen sensitization in China, the majority of them focus on one part of geography in China.3-5 In 2009, a study6 was conducted to estimate the prevalence of common aeroallergens among patients with allergic asthma and/or rhinitis in mainland China. Although the study investigated the differences of the prevalence in different regions of China, it divided China into only four geographical regions, which may neglect detailed information about the characteristics of sensitization prevalence in different places in China. In that study, the skin prick test (SPT) was used to detect the sensitization to allergens. The method has low accuracy for positive results because it is heavily affected by certain factors, such as the skill of the tester, reagent used, and interpretation of results. Our research has the following different characteristics compared with previous studies: (a) covering a variety of allergic diseases, (b) exploring both aeroallergens and food allergens simultaneously, (c) including a large set of data from all the seven regions of mainland China, and (d) using an internationally recognized method of sIgE testing, ImmunoCAP, to detect sensitization. These advantages may help us obtain more accurate and reliable results and conclusions. Here, we conducted a large multicenter study on the prevalence patterns of serum allergen-specific IgE (sIgE) sensitization to the four most common food allergens (ie, egg white, cow's milk, crab, and shrimp) and five aeroallergens (ie, house dust mite, German cockroach, tree pollen mix, mold mix, dog dander) among 44 156 patients with allergic symptoms in 52 cities from 26 provinces of all the seven geographical regions in mainland China from July 2015 to June 2018. These patients were evaluated by the physicians in the hospital and those who were suspected to have allergic diseases were then referred to have an sIgE sensitization test conducted by a certified third-party laboratory service provider with uniform and standardized procedures. This study was approved by the ethics committee of the First Affiliated Hospital of Guangzhou Medical University (Approval number: GYFYY-2017-18). Details about the methods were in the Appendix S1. Our study showed that the overall prevalence of positive sIgE responses to the 9 allergens across mainland China from the highest to the lowest was 33.74% for house dust mites, 24.5% for cockroaches, 19.97% for shrimp, 17.31% for crab, 11.62% for cow's milk, 10.92% for egg white, 9.35% for tree pollen mix, 4.02% for dog dander, and 3.92% for mold mix (Table 1). Our study confirmed that an observation that the positive cases in sIgE fell mainly in the two low classes (ie, classes 1 and 2) as shown in previous studies for certain specific areas in China3-5 was also held in all the seven regions in mainland China (Table 1). Our study revealed the distinctive patterns in the prevalence of allergen sensitization by region, gender, age, and season. Geographically, there is a significant difference in the prevalence among regions for all 9 allergens except for the mold mix (Table S1). House dust mites were the allergen with the highest prevalence of sensitization in all seven regions, with the highest in South China (40.79%) and the lowest in Northeast China (11.21%). Allergies to German cockroaches had a higher prevalence in southern regions (Southwest China, South China, and East China) than in northern regions (North China and Northeast China). The prevalence of sIgE responses to dog dander was the highest in North China and was very close to each other in the southern regions. The prevalence of the egg white and milk in Central China, East China, and South China was higher than in Southwest China, North China, and Northeast China, which means that patients living in eastern, coastal, and/or southern areas were more sensitive to egg white and cow's milk. The prevalence of crab and shrimp sensitization in Southwest China and South China was higher than that in the northern regions (North China and Northeast China). The difference in sensitization between crab and shrimp is small although people in different regions of China may have different preference in eating crab or shrimp (Table S1). The heatmap (Figure 1) displays the distribution of the prevalence of the sIgE response to allergens in different regions of mainland China. The prevalence of sensitization to all nine allergens was higher overall in males than in females significantly (Table 1 and Figure S1) although that may not be true in each age group for each allergen as shown in the forest plot in Figure S1. Our study showed that house dust mite, German cockroach, tree pollen, dog dander, crab, and shrimp had a prevalence pattern by age that the prevalence grows continuously as the age increases before and during the teenage period and then decreases continuously as the age increases after the teenage period ends whereas egg white and cow's milk had a pattern that the prevalence in the toddlers is the highest and then decrease continuously as the age increases (Figure S2). Mold had a pattern essentially from the mixture of these two patterns mainly caused by the different prevalence patterns in females and males (Figures S2 and S3). Our study further showed that the peak of prevalence of house dust mite, German cockroach, tree pollen mix, dog dander, crab, and shrimp moved roughly from late teenage to early teenage when middle/high sIgE classes (ie, classes 3-6) instead of all classes (ie, classes 1-6) were considered (Figures S2 and S4). This move was clearer in females as compared to males (Figures S3 and S5). Figure S6 displays the prevalence pattern of allergens by month across years. The prevalence of dog dander and mold mix was very stable across months; however, the prevalence of other allergens fluctuated from January to December. The prevalence of house dust mites, German cockroach, shrimp, and crab were higher in the summer months (from June to August) than in other months. The prevalence of tree pollen mix for classes 1-6 had two clearly high peaks in April and October, respectively; however, the peak in October disappeared when only classes 3-6 are considered. We believe this is the first large study to investigate the prevalence of allergen sensitization in the patients with allergic symptoms from all the seven geographic regions of mainland China. Based on this study, we found that the prevalence of sIgE sensitization to allergens displayed distinctive patterns among regions, gender, age groups, and seasons. The reasons for these patterns may include lifestyle factors, socioeconomic factors, genetic predispositions, climate, sexual hormones, and cross-reactivity.3, 4, 6-9 Please refer to the Appendix S1 for the detailed discussion on the factors that influenced these variations. Our findings may help clinicians find effective individualized treatments for unique patient groups and direct researchers to conduct further studies on the epidemiology of allergic diseases. This study was supported by the University of Macau (grant numbers: FHS-CRDA-029-002-2017, EF005/FHS-ZXH/2018/GSTIC and MYRG2018-00071-FHS), the Science and Technology Development Fund, Macau SAR (File no. 0004/2019/AFJ and 0011/2019/AKP), the National Natural Science Foundation of China (81802076 and 81871736), the National Key Technology R&D Program (2018YFC1311902), the Guangdong Science and Technology Foundation (2019B030316028), the Guangzhou Municipal Health Foundation (20191A011073), and the Guangzhou Science and Technology Foundation (201804020043). Dr Luo has nothing to disclose. Dr Wang has nothing to disclose. Dr Zhang has nothing to disclose. Dr Zheng has nothing to disclose. Dr Leng has nothing to disclose. Dr Li has nothing to disclose. Dr Liu has nothing to disclose. Dr Sun has nothing to disclose. Dr Zhang has nothing to disclose. The authors declare that they have no conflicts of interest. 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