It is known that small airway disease is present across all asthma severities; however, its prevalence and clinical characteristics in cough variant asthma (CVA) have not been fully illuminated. A total of 77 CVA patients with preserved proximal airway function (FEV1/FVC > 70%) were enrolled in this study. The correlation between forced expiratory flow at 50% (FEF50%) and FEF25–75% in the CVA population was first evaluated. FEF50% was determined to be an easy and feasible parameter for identifying small airway disease. CVA with small airway disease is defined as FEF50% < 70%, whereas CVA with normal small airways is identified as FEF50% > 70%. Demographic features, clinical characteristics, lung function and induced sputum test results were determined at the initial visit and at the final visit 1 year later. FEF50% is a good marker for small airway disease. The cutoff value of 70% is more sensitive than the previously published 60% for identifying more patients with small airway problems early. Nearly half of the CVA population (45.4%) in our cohort had small airway disease. In both group, symptoms improved greatly after anti-asthmatic treatment. Interestingly, the changes in symptom scores [Asthma Control Test (ACT) and ACQ] were even greater in the CVA with small airway disease group than in the control group because of the higher medication usage in this subpopulation in real life. However anti-asthmatic therapy can not reverse small airway dysfunction. At last visit, FEF50% of CVA with small airway diseases was 57.2% ± 10.5%, still much lower than the control group (FEF50% = 92.6% ± 16.5%). In our cohort, nearly half of the CVA population had small airway disease. Their demographic features, clinical characteristics, airway eosinophils and drug responsiveness were quite similar between two groups, which means these indices can not be used as markers to identify small airway obstruction. We found FEF50% is an easy and feasible marker for early identification. Regular anti-asthmatic medication helped to improve clinical scores in patients with small airway disease, but the obstruction could not be reversed over 1-year period.

中文翻译：

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咳嗽变异性哮喘伴小气道病变的临床及肺功能变化

众所周知，所有哮喘严重程度都存在小气道疾病；然而，其在咳嗽变异性哮喘 (CVA) 中的患病率和临床特征尚未完全阐明。本研究共招募了 77 名近端气道功能保留 (FEV1/FVC > 70%) 的 CVA 患者。首先评估了 CVA 人群中 50% (FEF50%) 和 FEF25-75% 的用力呼气流量之间的相关性。FEF50% 被确定为用于识别小气道疾病的简单可行的参数。小气道疾病的 CVA 定义为 FEF50% < 70%，而小气道正常的 CVA 定义为 FEF50% > 70%。人口学特征、临床特征、肺功能和诱导痰试验结果在初次就诊和 1 年后的最后一次就诊时确定。FEF50% 是小气道疾病的良好标志物。对于早期发现更多有小气道问题的患者，70% 的临界值比之前公布的 60% 更敏感。我们队列中近一半的 CVA 人群（45.4%）患有小气道疾病。两组在抗哮喘治疗后症状均有明显改善。有趣的是，CVA 小气道疾病组的症状评分 [哮喘控制测试 (ACT) 和 ACQ] 的变化甚至比对照组更大，因为在现实生活中这个亚群的药物使用率更高。然而抗哮喘治疗不能逆转小气道功能障碍。末次就诊时，小气道病变 CVA 的 FEF50% 为 57.2% ± 10.5%，仍远低于对照组（FEF50% = 92.6% ± 16.5%）。在我们的队列中，近一半的 CVA 人群患有小气道疾病。两组的人口统计学特征、临床特征、气道嗜酸性粒细胞和药物反应性非常相似，这意味着这些指标不能作为识别小气道阻塞的标志物。我们发现 FEF50% 是一种简单可行的早期识别标记。常规抗哮喘药物有助于改善小气道疾病患者的临床评分，但阻塞在 1 年内无法逆转。