BACKGROUND Asthma diagnosis in children is occasionally challenging, and the issue of undiagnosed asthma before adolescence has been poorly studied in Japan. The present study was conducted to investigate the possible presence of undiagnosed asthma in the general population of children living in a rural area of Japan. METHODS The participants comprised 120 fourth graders aged 9-10 years (boys/girls: 63/57) attending five elementary schools in Yawatahama, Ehime, Japan. All the children underwent respiratory function tests and fraction of exhaled nitric oxide (FeNO) measurements. Based on the results of a questionnaire, the children were also categorized into groups depending on their allergic diseases.The authors assessed the results of both the respiratory function tests and the FeNO measurements for children who were classified into the nonallergic group. RESULTS A total of 76 (63%) children, who completed the tests appropriately, were included in the analysis. According to the report, among the 24 children in the nonallergic group, six (25%) showed abnormalities in respiratory tests. One had an abnormal % forced vital capacity (%FVC; <80%), three had abnormalities in both forced expiratory volume in 1 sec (FEV1)/FVC (<80%) and % maximal mid-expiratory flow (<65%), three had concave flow-volume curves, and one had a high FeNO measurement (41 ppb). CONCLUSION A certain proportion of Japanese elementary school children, categorized as having no allergy, showed respiratory function test abnormalities. A follow-up study is needed to determine the prognosis and outcomes of the children with these abnormalities.

中文翻译：

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日本儿童可能存在未确诊的哮喘。

背景儿童哮喘诊断有时具有挑战性，而且在日本对青春期前未确诊的哮喘问题进行的研究很少。本研究旨在调查生活在日本农村地区的普通儿童人群中可能存在未确诊的哮喘。方法 参与者包括 120 名 9-10 岁的四年级学生（男孩/女孩：63/57），就读于日本爱媛县八幡滨的五所小学。所有儿童都接受了呼吸功能测试和呼出气一氧化氮 (FeNO) 分数测量。根据问卷调查的结果，这些儿童还根据他们的过敏性疾病进行分组。作者评估了分类为非过敏组儿童的呼吸功能测试和 FeNO 测量结果。结果 共有 76 名 (63%) 正确完成测试的儿童被纳入分析。报告称，在非过敏组的 24 名儿童中，有 6 名（25%）出现呼吸测试异常。1 人用力肺活量百分比异常 (%FVC; <80%)，3 人 1 秒用力呼气量 (FEV1)/FVC (<80%) 和最大呼气中流量百分比 (<65%) 均异常，三个具有凹流量-体积曲线，一个具有高 FeNO 测量值 (41 ppb)。结论 一定比例的日本小学生，被归类为没有过敏，表现出呼吸功能测试异常。