a Kyung Hee University School of Medicine , Department of Pulmonology and Critical Care Medicine , Seoul , Republic of Korea. b The Catholic University of Korea , Department of Internal Medicine, Seoul St Mary's Hospital, College of Medicine , Seoul , Republic of Korea. c Kyung Hee Univerisity Hospital at Gangdong , Department of Pulmonary and Critical Care Medicine , Seoul , Republic of Korea. d Soonchunhyang University Bucheon Hospital , Department of Internal Medicine , Bucheon , Republic of Korea. e Hallym University Sacred Heart Hospital , Department of Internal Medicine , Seoul , Republic of Korea. f College of Medicine, Korea University , Department of Internal Medicine , Seoul , Republic of Korea. g Chung Ang University Hospital Ringgold Standard Institution , Internal Medicine, Seoul , Republic of Korea.