Background: Respiratory pathogen infections and air pollution are main causes of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Air pollution has a direct effect on the airway epithelial barrier and the immune system, which can have an influence on infection. However, studies on the relationship between respiratory infections and air pollutants in severe AECOPD are limited. Thus, the objective of this study was to investigate the correlation between air pollution and respiratory pathogen in severe AECOPD. Methods: This multicenter observational study was conducted by reviewing electronic medical records of patients with AECOPD at 28 hospitals in South Korea. Patients were divided into four groups according to the comprehensive air-quality index (CAI) used in Korea. Identification rates of bacteria and viruses of each group were analyzed. Results: Viral pathogens were identified in 270 (36.7%) of 735 patients. Viral identification rate was different (P = 0.012) according to air pollution. Specifically, the virus detection rate was 55.9% in the group of CAI ‘D’ with the highest air pollution. It was 24.4% in the group of CAI ‘A’ with the lowest air pollution. This pattern was clearly seen for influenza virus A (P = 0.042). When further analysis was performed with particulate matter (PM), the higher/lower the PM level, the higher/lower the virus detection rate. However, no significant difference was found in the analysis related to bacteria. Conclusion Air pollution may make COPD patients more susceptible to respiratory viral infections, especially influenza virus A. Thus, on days with poor air quality, COPD patients need to be more careful about respiratory infections.

Background: The Global Initiative for Chronic Obstructive Lung Disease (GOLD) update 2023 proposed new definitions of chronic obstructive pulmonary disease (COPD) and COPD exacerbation. However, an agreement on the definitions has not been made, either internationally or domestically. This study aimed to reach an agreement between experts on the new definitions of COPD and COPD exacerbation in South Korea. Methods: A modified Delphi method was used to make an agreement on the definitions of COPD and COPD exacerbation proposed by the GOLD update 2023. We performed two rounds of the survey including 15 Korean experts on COPD, asthma, and tuberculosis. Results: More than two-thirds of the experts agreed on 12 of the 13 statements related to the definitions of COPD and COPD exacerbation in the two rounds of the survey. The experts agreed on the definitions of COPD and COPD exacerbation that should be revised in line with the definitions proposed by the GOLD update 2023. However, the experts showed an uncertain opinion on the statement that the definition of COPD includes patients with persistent airflow obstruction due to bronchiectasis. Conclusion Based on this Delphi survey, experts’ agreement was made on the definitions of COPD and COPD exacerbation proposed by the GOLD update 2023.

Background: Because the etiologies of bronchiectasis and related diseases vary significantly among different regions and ethnicities, this study aimed to develop a diagnostic bundle for bronchiectasis in South Korea. Methods: A modified Delphi method was used to develop expert consensus statements on a diagnostic bundle for bronchiectasis in South Korea. Initial statements proposed by a core panel, based on international bronchiectasis guidelines, were discussed in an online meeting and two email surveys by a panel of experts (≥70% agreement). Results: The study involved 21 expert participants, and 30 statements regarding a diagnostic bundle for bronchiectasis were classified as recommended, conditional, or not recommended. The consensus statements of the expert panel were as follows: A standardized diagnostic bundle is useful in clinical practice; diagnostic tests for specific diseases, including immunodeficiency and allergic bronchopulmonary aspergillosis, are necessary when clinically suspected; initial diagnostic tests, including sputum microbiology and spirometry, are essential in all patients with bronchiectasis, and patients suspected with rare causes such as primary ciliary dyskinesia should be referred to specialized centers. Conclusion Based on this Delphi survey, expert consensus statements were generated including specific diagnostic, laboratory, microbiological, and pulmonary function tests required to manage patients with bronchiectasis in South Korea.

Background: Although respiratory tract infection is one of the most important factors triggering acute exacerbation of chronic obstructive pulmonary disease (AE-COPD), limited data are available to suggest an epidemiologic pattern of microbiology in South Korea. Methods: A multicenter observational study was conducted between January 2015 and December 2018 across 28 hospitals in South Korea. Adult patients with moderate-to-severe acute exacerbations of COPD were eligible to participate in the present study. The participants underwent all conventional tests to identify etiology of microbial pathogenesis. The primary outcome was the percentage of different microbiological pathogens causing AE-COPD. A comparative microbiological analysis of the patients with overlapping asthma–COPD (ACO) and pure COPD was performed. Results: We included 1,186 patients with AE-COPD. Patients with pure COPD constituted 87.9% and those with ACO accounted for 12.1%. Nearly half of the patients used an inhaled corticosteroid-containing regimen and one-fifth used systemic corticosteroids. Respiratory pathogens were found in 55.3% of all such patients. Bacteria and viruses were detected in 33% and 33.2%, respectively. Bacterial and viral coinfections were found in 10.9%. The most frequently detected bacteria were Pseudomonas aeruginosa (9.8%), and the most frequently detected virus was influenza A (10.4%). Multiple bacterial infections were more likely to appear in ACO than in pure COPD (8.3% vs. 3.6%, p=0.016). Conclusion Distinct microbiological patterns were identified in patients with moderate-to-severe AE-COPD in South Korea. These findings may improve evidence-based management of patients with AE-COPD and represent the basis for further studies investigating infectious pathogens in patients with COPD.

Background/Aims: We evaluated the feasibility and long-term efficacy of the combination of cytarabine, idarubicin, and all-trans retinoic acid (ATRA) for treating patients with newly diagnosed acute promyelocytic leukemia (APL). Methods: We included 87 patients with newly diagnosed acute myeloid leukemia and a t(15;17) or promyelocytic leukemia/retinoic acid receptor alpha (PML-RARα) mutation. Patients received 12 mg/m2/day idarubicin intravenously for 3 days and 100 mg/m2/day cytarabine for 7 days, plus 45 mg/m2/day ATRA. Clinical outcomes included complete remission (CR), relapse-free survival (RFS), overall survival (OS), and the secondary malignancy incidence during a 20-year follow-up. Results: The CR, 10-year RFS, and 10-year OS rates were 89.7%, 94.1%, and 73.8%, respectively, for all patients. The 10-year OS rate was 100% for patients that achieved CR. Subjects were classified according to the white blood cell (WBC) count in peripheral blood at diagnosis (low-risk, WBC < 10,000/mm3; high-risk, WBC ≥ 10,000/mm3). The low-risk group had significantly higher RFS and OS rates than the high-risk group, but the outcomes were not superior to the current standard treatment (arsenic trioxide plus ATRA). Toxicities were similar to those observed with anthracycline plus ATRA, and higher than those observed with arsenic trioxide plus ATRA. The secondary malignancy incidence after APL treatment was 2.7%, among the 75 patients that achieved CR, and 5.0% among the 40 patients that survived more than 5 years after the APL diagnosis. Conclusions Adding cytarabine to anthracycline plus ATRA was not inferior to anthracycline plus ATRA alone, but it was not comparable to arsenic trioxide plus ATRA. The probability of secondary malignancy was low.

Background: The impact of reflux esophagitis on the decline of lung function has been rarely reported. This study was performed to evaluate the association between erosive reflux esophagitis and lung function changes. Methods: We included patients with normal lung function who underwent esophagogastroduodenoscopy for health screening from a health screening center. Patients with persistent erosive reflux esophagitis on two discrete endoscopic examinations were designated as the erosive reflux esophagitis group. We also selected patients without erosive reflux esophagitis and matched them 1:4 with patients from the erosive reflux esophagitis group. We estimated annual forced expiratory volume in 1 second (FEV1 ) and forced vital capacity (FVC) changes from baseline and compared these estimates by the linear mixed regression model. We also estimated the biannual incidence of chronic obstructive pulmonary disease (COPD). Results: In total, 1,050 patients (210 patients with erosive reflux esophagitis, and 840 matched controls) were included. The median follow-up duration for spirometry was six years. In patients with erosive reflux esophagitis, mild reflux esophagitis (A grade) was most common (165 patients, 78.6%). The adjusted annual FEV1 change in patients with erosive reflux esophagitis was −51.8 mL/yr, while it decreased by 46.8 mL/yr in controls (P = 0.270).The adjusted annual FVC decline was similar between the two groups (−55.8 vs. −50.5 mL/ yr, P = 0.215). The estimated COPD incidence during the follow-up period was not different between the erosive reflux esophagitis and control groups. Conclusion In patients with normal lung function, the presence of erosive reflux esophagitis did not affect the annual declines in FEV1 or FVC.

Background: The impact of reflux esophagitis on the decline of lung function has been rarely reported. This study was performed to evaluate the association between erosive reflux esophagitis and lung function changes. Methods: We included patients with normal lung function who underwent esophagogastroduodenoscopy for health screening from a health screening center. Patients with persistent erosive reflux esophagitis on two discrete endoscopic examinations were designated as the erosive reflux esophagitis group. We also selected patients without erosive reflux esophagitis and matched them 1:4 with patients from the erosive reflux esophagitis group. We estimated annual forced expiratory volume in 1 second (FEV1 ) and forced vital capacity (FVC) changes from baseline and compared these estimates by the linear mixed regression model. We also estimated the biannual incidence of chronic obstructive pulmonary disease (COPD). Results: In total, 1,050 patients (210 patients with erosive reflux esophagitis, and 840 matched controls) were included. The median follow-up duration for spirometry was six years. In patients with erosive reflux esophagitis, mild reflux esophagitis (A grade) was most common (165 patients, 78.6%). The adjusted annual FEV1 change in patients with erosive reflux esophagitis was −51.8 mL/yr, while it decreased by 46.8 mL/yr in controls (P = 0.270).The adjusted annual FVC decline was similar between the two groups (−55.8 vs. −50.5 mL/ yr, P = 0.215). The estimated COPD incidence during the follow-up period was not different between the erosive reflux esophagitis and control groups. Conclusion In patients with normal lung function, the presence of erosive reflux esophagitis did not affect the annual declines in FEV1 or FVC.

BACKGROUND: Chronic cough is defined as a cough lasting more than 8 weeks and socio-economic burden of chronic cough is enormous. The characteristics of chronic cough in Korea are not well understood. The Korean Academy of Tuberculosis and Respiratory Diseases (KATRD) published guidelines on cough management in 2014. The current study evaluated the clinical characteristics of chronic cough in Korea and the efficacy of the KATRD guidelines. METHODS: This was a multi-center, retrospective observational study conducted in Korea. The participants were over 18 years of age. They had coughs lasting more than 8 weeks. Subjects with current pulmonary diseases, smokers, ex-smokers with more than 10 pack-years or who quit within the past 1 year, pregnant women, and users of cough-inducing medications were excluded. Evaluation and management of cough followed the KATRD cough-management guidelines. RESULTS: Participants with chronic cough in Korea showed age in the late forties and cough duration of more than 1 year. Upper airway cough syndrome was the most common cause of cough, followed by cough-variant asthma (CVA). Gastro-esophageal reflux diseases and eosinophilic bronchitis were less frequently observed. Following the KATRD cough-management guidelines, 91.2% of the subjects improved after 4 weeks of treatment. Responders were younger, had a longer duration of cough, and an initial impression of CVA. In univariate and multivariate analyses, an initial impression of CVA was the only factor related to better treatment response. CONCLUSION The causes of chronic cough in Korea differed from those reported in other countries. The current Korean guidelines proved efficient for treating Korean patients with chronic cough.

BACKGROUND: Chronic cough is defined as a cough lasting more than 8 weeks and socio-economic burden of chronic cough is enormous. The characteristics of chronic cough in Korea are not well understood. The Korean Academy of Tuberculosis and Respiratory Diseases (KATRD) published guidelines on cough management in 2014. The current study evaluated the clinical characteristics of chronic cough in Korea and the efficacy of the KATRD guidelines. METHODS: This was a multi-center, retrospective observational study conducted in Korea. The participants were over 18 years of age. They had coughs lasting more than 8 weeks. Subjects with current pulmonary diseases, smokers, ex-smokers with more than 10 pack-years or who quit within the past 1 year, pregnant women, and users of cough-inducing medications were excluded. Evaluation and management of cough followed the KATRD cough-management guidelines. RESULTS: Participants with chronic cough in Korea showed age in the late forties and cough duration of more than 1 year. Upper airway cough syndrome was the most common cause of cough, followed by cough-variant asthma (CVA). Gastro-esophageal reflux diseases and eosinophilic bronchitis were less frequently observed. Following the KATRD cough-management guidelines, 91.2% of the subjects improved after 4 weeks of treatment. Responders were younger, had a longer duration of cough, and an initial impression of CVA. In univariate and multivariate analyses, an initial impression of CVA was the only factor related to better treatment response. CONCLUSION The causes of chronic cough in Korea differed from those reported in other countries. The current Korean guidelines proved efficient for treating Korean patients with chronic cough.

Background/Aims: Despite increasing awareness of the burden of chronic obstructive pulmonary disease (COPD) in women, knowledge regarding gender differences in COPD outcomes is limited. Therefore, we aimed to evaluate whether COPD outcomes, including exacerbations, lung , and symptoms differ by gender. Methods: We recruited patients with COPD from two Korean multicenter prospective cohorts. After propensity score matching, the main outcome, the incidence of moderate or severe exacerbations was analyzed using a negative binomial regression model. We also assessed changes in lung function and symptom scores including the St. George’s respiratory questionnaire for COPD (SGRQ-C), COPD assessment test (CAT), and the modified Medical Research Council (mMRC) dyspnea score. Results: After propensity score matching, 74 women and 74 men with COPD were included. The incidence rates of exacerbations in women and men were not significantly different (incidence rate ratio, 1.49; 95% confidence interval [CI], 0.88 to 2.54). There was no significant difference in the incidence rates adjusted for medication possession ratios of long-acting muscarinic antagonists, long-acting β-agonists, and inhaled corticosteroids during the follow-up period (incidence rate ratio, 1.47; 95% CI, 0.86 to 2.52). Rates of decline in post-bronchodilator forced expiratory volume in 1 second and forced vital capacity did not differ between women and men during 48 months of follow-up. The changes in scores on the SGRQ-C, CAT, and mMRC Questionnaire in women were also similar to those in men. Conclusions We observed no gender differences in the rate of exacerbations of COPD in a prospective longitudinal study. Further studies are needed to confirm these findings in the general COPD population.