title: Differences in the etiology of community-acquired pneumonia according to site of care: a population-based study.
abstract: BACKGROUND
  A few population-based studies assessing the etiology of community-acquired pneumonia in both hospitalized and ambulatory patients, with special emphasis on the etiologic role of viral infections, have been reported. The purpose of this study was to assess microbiological differences according to initial site of care in patients with community-acquired pneumonia.
  
  
  METHODS
  We studied 496 patients > 14 years of age collected from the study samples of three population-based studies carried out in the same geographical area ("Maresme" region in the Mediterranean coast in Barcelona, Spain) with the same methodology over an 8-year period (1987-1995).
  
  
  RESULTS
  Fifty-six percent of patients were hospitalized and 44% were treated at home. Of the 474 patients with etiological evaluation, 195 patients had an identifiable etiology (overall diagnostic yield 41%). Streptococcus pneumoniae was the most common causative organism. Viral infection was diagnosed in 26.5% of hospitalized patients vs. 13.2% of ambulatory patients (P=0.03). Twenty-five percent of the 68 patients with documented etiology treated at home had Chlamydia pneumoniae infection compared with 14.3% of those treated in the hospital. Ten percent of hospitalized patients had pneumonia caused by two pathogens compared with 9.7% of ambulatory patients. The association of viruses and bacteria was the most frequent cause of dual infection (79% inpatients, 67% outpatients).
  
  
  CONCLUSIONS
  This study has provided information on etiology of community-acquired pneumonia in hospitalized patients and in patients treated at home. A considerable proportion of patients had viral pneumonia, frequently requiring hospital admission for inpatient care.
authors.affiliation: Critical Care Unit, Hospital de Mataró, Universitat Autònoma de Barcelona, Mataró, Barcelona, Spain. jalmirall@csdm.cat
authors.forename: Jordi
authors.initials: J
authors.lastname: Almirall
authors.forename: Ramon
authors.initials: R
authors.lastname: Boixeda
authors.forename: Ignasi
authors.initials: I
authors.lastname: Bolíbar
authors.forename: Josep
authors.initials: J
authors.lastname: Bassa
authors.forename: Goretti
authors.initials: G
authors.lastname: Sauca
authors.forename: Josep
authors.initials: J
authors.lastname: Vidal
authors.forename: Mateu
authors.initials: M
authors.lastname: Serra-Prat
authors.forename: Xavier
authors.initials: X
authors.lastname: Balanzó
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018893:Bronchoalveolar Lavage / Q000379:methods; D017714:Community-Acquired Infections / Q000209:etiology*; D005260:Female; D006699:Home Care Services / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000209:etiology*