Ohwada Akihiko, Kitaoka Hiroko
Ohwada Clinic, Ichikawa, Japan.
Division of Respiratory Medicine, Juntendo University Faculty of Medicine and Graduate School of Medicine, Tokyo, Japan.
J Thorac Dis. 2024 Sep 30;16(9):5580-5590. doi: 10.21037/jtd-24-868. Epub 2024 Aug 30.
Cough variant asthma (CVA) is characterized by cough as a sole symptom and normal pulmonary function. However, it is unclear whether CVA really common among asthmatic patients with normal forced expiratory volume in 1 second (FEV1). The aim of this study was to evaluate the incidence of cough alone symptom among the subjects with normal FEV1 and to evaluate their differences from ordinary asthmatic subjects.
We defined normal FEV1 as ≥90% predicted based on the article of Kotti GH. Of the patients with normal FEV1, we chose subjects without wheeze, and the duration of cough was not to ask, since the symptoms often occurred with acute exacerbation and timing of visiting a doctor depended on each patient's perception. Test for airway hyperresponsiveness was not performed in this study. Visual analogue scale (VAS) scores for cough and dyspnea, FEV1, and fractional exhaled nitric oxide (FeNO) responsiveness to inhaled corticosteroid (ICS)/long-acting beta2 agonist (LABA) treatment were compared in patients with normal FEV1 and with low FEV1 <90%. Correlations of changes in symptoms with changes of FEV1, FeNO, peripheral eosinophil count, and serum immunoglobulin E (IgE) at single time point were also examined in each group and in overall patients.
The participants were 329 physician-diagnosed treatment-naive patients with asthma who were divided into 187 in normal FEV1 and 142 in low FEV1 groups. Cough without dyspnea was present in 16 patients (8.6%) in the normal FEV1 group, suggesting candidates for CVA in this analysis were quite few. Improvement in symptoms after treatment was similar between both groups. But VAS scores of dyspnea were still higher in the low FEV1 group. The degree of improvement in FEV1 after ICS/LABA treatment was less in the normal FEV1 group than in the low FEV1 group, but was still evident. Peripheral eosinophil count, serum IgE, and FeNO values before treatment were lower in the normal FEV1 group. In overall patients, improvements of symptoms after treatment were significantly correlated with FEV1 changes. Improvement of dyspnea was also significantly related to peripheral eosinophil count and change of FeNO, whereas improvement of cough was not related to these T helper 2 (Th2) response markers.
Candidates for CVA among the patients with asthma with predicted FEV1 ≥90% were few. Participants with normal FEV1 respond well to ICS/LABA treatment for improvement of symptom. The change of FEV1 after treatment, and the pre-treatment blood eosinophil count, serum IgE, and FeNO were lower in normal FEV1 cases than in low FEV1 cases. These observations suggest asthmatic patients with normal FEV1, including candidates for CVA having just common mild asthma. In overall participants, symptoms of cough and dyspnea were similar, but were not identical in relation to the Th2 background.
咳嗽变异性哮喘（CVA）以咳嗽为唯一症状且肺功能正常为特征。然而，在一秒用力呼气容积（FEV1）正常的哮喘患者中，CVA是否真的常见尚不清楚。本研究的目的是评估FEV1正常的受试者中单纯咳嗽症状的发生率，并评估他们与普通哮喘受试者的差异。
根据Kotti GH的文章，我们将FEV1正常定义为≥预测值的90%。在FEV1正常的患者中，我们选择无喘息症状的受试者，且不询问咳嗽持续时间，因为症状常随急性加重而出现，就诊时间取决于每个患者的感受。本研究未进行气道高反应性测试。比较了FEV1正常和FEV1<90%的患者在咳嗽和呼吸困难的视觉模拟量表（VAS）评分、FEV1以及吸入糖皮质激素（ICS）/长效β2受体激动剂（LABA）治疗后的呼出一氧化氮分数（FeNO）反应性。还在每组及所有患者中检查了单个时间点症状变化与FEV1、FeNO、外周嗜酸性粒细胞计数和血清免疫球蛋白E（IgE）变化的相关性。
参与者为329例经医生诊断的初治哮喘患者，分为FEV1正常组187例和FEV1低组142例。FEV1正常组有16例患者（8.6%）无呼吸困难的咳嗽，表明本分析中CVA的候选者相当少。两组治疗后症状改善情况相似。但FEV1低组的呼吸困难VAS评分仍较高。ICS/LABA治疗后FEV1的改善程度在FEV1正常组低于FEV1低组，但仍很明显。FEV1正常组治疗前的外周嗜酸性粒细胞计数、血清IgE和FeNO值较低。在所有患者中，治疗后症状的改善与FEV1变化显著相关。呼吸困难的改善也与外周嗜酸性粒细胞计数和FeNO变化显著相关，而咳嗽的改善与这些辅助性T细胞2（Th2）反应标志物无关。
预测FEV1≥90%的哮喘患者中CVA的候选者很少。FEV1正常的参与者对ICS/LABA治疗改善症状反应良好。治疗后FEV1的变化以及治疗前血嗜酸性粒细胞计数、血清IgE和FeNO在FEV1正常的病例中低于FEV1低的病例。这些观察结果表明，FEV1正常的哮喘患者，包括CVA候选者，具有普通轻度哮喘。在所有参与者中，咳嗽和呼吸困难症状相似，但与Th2背景的关系并不相同。
