Abstract: Background　High concentration of serum 25-hydroxyvitamin D （25（OH）D） can maintain the normal metabolism of 25（OH）D receptors in human skeletal exocytes，which is closely related to the blood circulation system，respiratory system，connective tissue，autoimmunity and development of tumors.Some studies have shown that supplementation of 25（OH）D3 at 4 000 U per day can significantly reduce the incidence of infection symptoms，number of pathogenic bacteria in nasal swabs and the consumption of antibiotics.It can also reduce the incidence of recurrent respiratory tract infection in children due to imperfect immune function.In this study，we aimed to validate the association between the concentration of 25 （OH） D，immune function and recurrent respiratory tract infection in children.Objective　To evaluate the distribution of serum 25（OH）D concentration in children with different levels of immunoglobulin G （IgG） and M （IgM），and to further analyze the association between 25（OH）D and hepatitis B antibody titers （anti-HBs） as well as recurrent respiratory infection.Methods　A total of 146 children with recurrent respiratory infection at First Affiliated Hospital of Anhui Medical University from August 2016 to October 2018 were included in the study.According to age，patients were divided into different groups：0-<2 years group，2-<6 years group，6-<12 years group and 12-16 years group.Serum 25（OH）D level was assessed between different groups.Additionally，patients were grouped by the levels of serum IgG and IgM：79 cases in reduced IgG group，38 cases in normal IgG group and 30 cases in elevated IgG group，92 cases in reduced IgM group，29 cases in normal IgM group and 25 cases in elevated IgM group.Serum 25 （OH） D was evaluated in different groups to determine the relationship between the levels of serum 25（OH）D and IgG，IgM.Poisson regression analysis was used to evaluate the association between serum 25（OH）D concentration and the number of repeated respiratory infection in children.Results　Compared to 2-<6 years group，6-<12 years group and 12-16 years group，0-<2 years group had higher serum 25（OH）D levels（q=5.202，6.030，8.432，P <0.001）．Serum 25（OH）D levels in 2-<6 years group and 6-<12 years group were higher than that in 12-16 years group（q=5.317，5.559，P<0.05）．Result of Poisson regression showed，increased level of serum 25（OH）D was negatively associated with the number of repeated respiratory infection in children 〔FR=0.94，95%CI（0.89，1.02），P=0.048〕．Conclusion　Serum 25（OH）D concentration was no  correlation with serum anti-HBs titer，but negatively associated with the number of recurrent respiratory tract infection in children.

Key words: Respiratory tract infections, Vitamin D, Immunity, IgG, IgM, Anti-HBs titer

摘要： 背景　高水平的25-羟维生素D〔25（OH）D〕维持着人体骨骼系统外细胞25（OH）D受体的正常新陈代谢，与血液循环系统、呼吸系统、结缔组织及自身免疫疾病和肿瘤的发展密切相关，相关研究表明，每天补充4 000 U的25（OH）D3可显著减少免疫缺陷患儿的感染症状、鼻拭子中的致病菌数量、对抗生素的消耗，减少儿童由于免疫功能不完善导致反复呼吸道感染的发生。目的　对反复呼吸道感染儿童的血清25（OH）D水平在不同IgG和IgM水平患儿中的分布差异及与乙肝抗体（anti-HBs）滴度和反复呼吸道感染次数之间的关联性进行分析，为25（OH）D补充剂在减少儿童反复呼吸道感染中的实际应用提供线索。方法　选取2016年8月—2018年10月于安徽医科大学第一附属医院接受治疗的反复呼吸道感染患儿146例，根据年龄分为0~<2岁组、2~<6岁组、6~<12岁组、12~16岁组，比较各年龄组血清25（OH）D水平；根据研究对象的血清IgG、IgM水平分为IgG降低组79例、IgG正常组38例及IgG升高组30例，IgM降低组92例、IgM正常组29例及IgM升高组25例，比较各组间血清25（OH）D水平；采用泊松回归分析对血清25（OH）D水平与儿童反复呼吸道感染次数进行关联性分析。结果　0~<2岁组血清25（OH）D水平高于2~<6岁组、6~<12岁组和12~16岁组（q=5.202、6.030、8.432，P值均<0.001）；2~<6岁组和6~<12岁组血清25（OH）D水平高于12~16岁儿童（q=5.317、5.559，P值均<0.05）。泊松回归分析结果显示，血清25（OH）D水平与儿童反复呼吸道感染次数呈现负向关联〔FR=0.94，95%CI（0.89，1.02），P=0.048〕。结论　儿童的血清25（OH）D水平与血清anti-HBs滴度无相关关系，与反复呼吸道感染次数呈现负向关联。

关键词: 呼吸道感染, 维生素D, 免疫, IgG, IgM, anti-HBs滴度