title: Ventilator-associated pneumonia: caveats for benchmarking.
abstract: OBJECTIVE
  To determine the influence of using different denominators on risk estimates of ventilator-associated pneumonia (VAP).
  
  
  METHODS
  Prospective cohort study in the medical ICU of a large teaching hospital.
  
  
  METHODS
  All consecutive patients admitted for more than 48 h between October 1995 and November 1997.
  
  
  RESULTS
  We recorded all ICU-acquired infections using modified CDC criteria. VAP rates were reported per 1,000 patient-days, patient-days at risk, ventilator-days, and ventilator-days at risk. Of the 1,068 patients admitted, VAP developed in 106 (23.5%) of those mechanically ventilated. The incidence of the first episode of VAP was 22.8 per 1,000 patient-days (95% CI 18.7-27.6), 29.6 per 1,000 patient-days at risk (24.2-35.8), 35.7 per 1,000 ventilator-days (29.2-43.2), and 44.0 per 1,000 ventilator-days at risk (36.0-53.2). When considering all episodes of VAP (n=127), infection rates were 27.3 episodes per 1,000 ICU patient-days (95% CI 22.6-32.1) and 42.8 episodes per 1,000 ventilator-days (35.3-50.2).
  
  
  CONCLUSIONS
  The method of reporting VAP rates has a significant impact on risk estimates. Accordingly, clinicians and hospital management in charge of patient-care policies should be aware of how to read and compare nosocomial infection rates.
authors.affiliation: Infection Control Program, Department of Internal Medicine, University Hospitals of Geneva, 1211, Geneva 14, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Eggimann
authors.forename: Stéphane
authors.initials: S
authors.lastname: Hugonnet
authors.forename: Hugo
authors.initials: H
authors.lastname: Sax
authors.forename: Sylvie
authors.initials: S
authors.lastname: Touveneau
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Chevrolet
authors.forename: Didier
authors.initials: D
authors.lastname: Pittet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019985:Benchmarking; D003422:Critical Care / Q000379:methods / Q000592:standards; D003428:Cross Infection / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D005260:Female; D017052:Hospital Mortality; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D017053:Infection Control / Q000379:methods / Q000592:standards; D007362:Intensive Care Units; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D018570:Risk Assessment; D012307:Risk Factors; D013557:Switzerland / Q000453:epidemiology; D013997:Time Factors