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Fanny Wai San Ko,1 Ka Pang Chan,1 Joyce Ka Ching Ng,1 Jenny CL Ngai,1 Wing Ho Yip,1 Rachel Lai Ping Lo,1 Tat On Chan,2 David Shu Cheong Hui1 1Department of Medicine and Therapeutics, the Chinese University of Hong Kong, Hong Kong, People’s Republic of China; 2The Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, People’s Republic of ChinaCorrespondence: David Shu Cheong Hui, Department of Medicine and Therapeutics, the Chinese University of Hong Kong, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, NT, Hong Kong, Tel +852 35053128, Email dschui@cuhk.edu.hkBackground and Objective: Previous studies found that the fractional nitric oxide concentration in exhaled breath (FeNO) levels in healthy Chinese adults was higher than in White adults. More understanding of serial changes of FeNO levels with asthma control in a real-life clinical setting would be important to explore the utility of this biomarker in routine asthma management. This study assessed the FeNO levels of Chinese asthma subjects with different levels of asthma control and the serial changes with respect to the changes in asthma control over 1 year.Methods: A 12-month prospective study (subjects recruited between November 2019 and January 2021) with serial measurement of FeNO levels at baseline, 4, 8 and 12 months. Asthma control was assessed by the Global Initiative for Asthma classification, Asthma Control Test (ACT) and Asthma Control Questionnaire (ACQ).Results: Altogether, 136 subjects (mean age 51.51± 15.09 years, 46[33.8%] male) had successful baseline FeNO measurements. At baseline, the FeNO levels did not show a statistically significant difference for controlled, partly controlled and uncontrolled asthma according to GINA classification, ACT and ACQ. FeNO levels decreased with improving asthma control and stayed at similar levels with unchanged or worsening asthma control for all subjects. For subjects with baseline blood eosinophil levels ≥ 300 cells/μL(n=59), FeNO levels decreased with improving asthma control, stayed similar without change for asthma control and increased with worsening asthma control. Receiver operating characteristic (ROC) analysis with the highest area under curve (AUC) for changes in FeNO levels for improving asthma control was between ≤ − 10 to − 25 ppb at various time points in the 12-month study.Conclusion: Changes in FeNO levels over time were associated with changes in clinical asthma control, particularly in those with higher blood eosinophil count and are likely more useful than a single time point measurement in managing asthma.Keywords: asthma, FeNO, serial measurement

Fanny Wai-San Ko,1 Julie KL Wang,2 David SC Hui,1 Johnny WM Chan,3 Pik-Shan Cheung,4 Yiu-Cheong Yeung,5 Kit Man Sin,6 Mary Sau-Man Ip7 1Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, People’s Republic of China; 2Department of Medicine, Queen Mary Hospital, Hong Kong, People’s Republic of China; 3Department of Medicine, Queen Elizabeth Hospital, Hong Kong, People’s Republic of China; 4Department of Medicine, United Christian Hospital, Hong Kong, People’s Republic of China; 5Department of Medicine and Geriatrics, Princess Margaret Hospital, Hong Kong, People’s Republic of China; 6Department of Medicine, Tuen Mun Hospital, Hong Kong, People’s Republic of China; 7Department of Medicine, School of Clinical Medicine, The University of Hong Kong, Hong Kong, People’s Republic of ChinaCorrespondence: Mary Sau-Man Ip, Division of Respiratory Medicine, Department of Medicine, School of Clinical Medicine, The University of Hong Kong, 4/F, Professorial Block, Queen Mary Hospital, Pokfulam, Hong Kong, People’s Republic of China, Email msmip@hkucc.hku.hkBackground: Patients with severe asthma have higher total- and asthma-related health burden than those whose disease is not severe. Recent medical advances in biologic therapies allow better control of asthma characterized by type 2 inflammation.Objective: To study the prevalence of eosinophilic phenotype and IgE levels in Chinese with severe asthma, and the relationship of these type 2 characteristics with asthma control, exacerbations and lung function.Methods: This was a multicenter cross-sectional observational study in Hong Kong, in Chinese adults with asthma on Step 4 or 5 of GINA treatment. Their blood eosinophil counts and total IgE levels were measured, and the relationship of these phenotypic parameters to the number of exacerbations in the past 12 months, and to symptom control in the past 4 weeks, were investigated.Results: A total of 232 subjects were recruited from 6 centers. The mean age was 53.9± 12.9 years, with 86 (37.1%) male, and the duration of diagnosed asthma was 26.2± 15.7 years. A T-helper 2 (Th2) phenotype indicated by elevated eosinophils and/or IgE was present in 169 (72.8%) of patients. Of 232 patients, 43% had an eosinophilic phenotype (blood eosinophil count ≥ 300 cell/mm3), while 59% had high total IgE levels of > 100 IU/mL (overlap with eosinophilic phenotype in 30%) and 44% had IgE levels of > 150 IU/mL (overlap with eosinophilic phenotype in 22%). Subjects with eosinophilic phenotype and IgE > 150 IU/mL had a higher rate (1.8 times) of uncontrolled asthma compared with those without such a combination.Conclusion: In Chinese adults with severe asthma defined by the use of conventional maintenance medication regimens, the prevalence of Th2 inflammation is comparable to that reported from other ethnic populations. Those with both eosinophil count ≥ 300 cell/mm3 and high IgE levels > 150 IU/mL had a higher rate of uncontrolled asthma compared with those without a combination of these features.Keywords: asthma, Chinese, cross-sectional, eosinophils, Hong Kong, immunoglobulin E