title: A 1-year prospective study of the infectious etiology in patients hospitalized with acute exacerbations of COPD.
abstract: BACKGROUND
  Infection is a major cause of acute exacerbations of COPD (AECOPDs). We aimed to study the infectious etiology related to AECOPD.
  
  
  METHODS
  Patients admitted to an acute care hospital in Hong Kong with an AECOPD were recruited prospectively from May 1, 2004, to April 30, 2005. Sputum samples, nasopharyngeal aspirate (NPA) samples, and paired serology specimens were collected. Spirometry was performed with patients in the stable phase 2 to 3 months after hospital discharge.
  
  
  RESULTS
  There were 643 episodes of AECOPD among 373 patients. Their mean age was 75.3 years (SD, 7.9 years) with 307 male patients. The mean FEV(1) was 40.4% predicted (SD, 18.7% predicted), and the mean FEV(1)/FVC ratio was 58.4% (SD, 16.0%). Among sputum samples from the 530 episodes of AECOPD hospital admissions that were saved, 13.0%, 6.0%, and 5.5%, respectively, had positive growth of Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae. Among the 505 hospital admissions with patients who had NPA samples saved, 5.7%, 2.3%, 0.8%, and 0.8%, respectively, had influenza A, respiratory syncytial virus (RSV), influenza B, and parainfluenza 3 isolated from viral cultures. Paired serology test results revealed a fourfold rise in viral titers in 5.2%, 2.2%, and 1.4% of patients, respectively, for influenza A, RSV, and influenza B. Very severe airflow obstruction (stable-state spirometry) was associated with a higher chance of a positive sputum culture (FEV(1) >/= 30% predicted, 28.2%; FEV(1) < 30% predicted, 40.4%; p = 0.006).
  
  
  CONCLUSIONS
  H influenzae and influenza A were the most common etiologic agents in patients who were hospitalized with AECOPDs. More severe airflow obstruction was associated with a higher chance of a positive sputum culture finding.
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, 30-32 Ngan Shing St, Shatin, New Territories, Hong Kong, Peoples Republic of China. fannyko@cuhk.edu.hk
authors.forename: Fanny W S
authors.initials: FW
authors.lastname: Ko
authors.forename: Margaret
authors.initials: M
authors.lastname: Ip
authors.forename: Paul K S
authors.initials: PK
authors.lastname: Chan
authors.forename: Joan P C
authors.initials: JP
authors.lastname: Fok
authors.forename: Michael C H
authors.initials: MC
authors.lastname: Chan
authors.forename: Jenny C
authors.initials: JC
authors.lastname: Ngai
authors.forename: Doris P S
authors.initials: DP
authors.lastname: Chan
authors.forename: David S C
authors.initials: DS
authors.lastname: Hui
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D005260:Female; D005541:Forced Expiratory Volume; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D008297:Male; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology / Q000503:physiopathology*; D012141:Respiratory Tract Infections / Q000382:microbiology* / Q000503:physiopathology*; D013147:Spirometry; D013183:Sputum / Q000382:microbiology; D018709:Statistics, Nonparametric