title: Attributable mortality of ventilator-associated pneumonia: a meta-analysis of individual patient data from randomised prevention studies.
abstract: BACKGROUND
  Estimating attributable mortality of ventilator-associated pneumonia has been hampered by confounding factors, small sample sizes, and the difficulty of doing relevant subgroup analyses. We estimated the attributable mortality using the individual original patient data of published randomised trials of ventilator-associated pneumonia prevention.
  
  
  METHODS
  We identified relevant studies through systematic review. We analysed individual patient data in a one-stage meta-analytical approach (in which we defined attributable mortality as the ratio between the relative risk reductions [RRR] of mortality and ventilator-associated pneumonia) and in competing risk analyses. Predefined subgroups included surgical, trauma, and medical patients, and patients with different categories of severity of illness scores.
  
  
  RESULTS
  Individual patient data were available for 6284 patients from 24 trials. The overall attributable mortality was 13%, with higher mortality rates in surgical patients and patients with mid-range severity scores at admission (ie, acute physiology and chronic health evaluation score [APACHE] 20-29 and simplified acute physiology score [SAPS 2] 35-58). Attributable mortality was close to zero in trauma, medical patients, and patients with low or high severity of illness scores. Competing risk analyses could be done for 5162 patients from 19 studies, and the overall daily hazard for intensive care unit (ICU) mortality after ventilator-associated pneumonia was 1·13 (95% CI 0·98-1·31). The overall daily risk of discharge after ventilator-associated pneumonia was 0·74 (0·68-0·80), leading to an overall cumulative risk for dying in the ICU of 2·20 (1·91-2·54). Highest cumulative risks for dying from ventilator-associated pneumonia were noted for surgical patients (2·97, 95% CI 2·24-3·94) and patients with mid-range severity scores at admission (ie, cumulative risks of 2·49 [1·81-3·44] for patients with APACHE scores of 20-29 and 2·72 [1·95-3·78] for those with SAPS 2 scores of 35-58).
  
  
  CONCLUSIONS
  The overall attributable mortality of ventilator-associated pneumonia is 13%, with higher rates for surgical patients and patients with a mid-range severity score at admission. Attributable mortality is mainly caused by prolonged exposure to the risk of dying due to increased length of ICU stay.
  
  
  BACKGROUND
  None.
authors.affiliation: Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht, The Netherlands. mariannemelsen@gmail.com
authors.forename: Wilhelmina G
authors.initials: WG
authors.lastname: Melsen
authors.forename: Maroeska M
authors.initials: MM
authors.lastname: Rovers
authors.forename: Rolf H H
authors.initials: RH
authors.lastname: Groenwold
authors.forename: Dennis C J J
authors.initials: DC
authors.lastname: Bergmans
authors.forename: Christophe
authors.initials: C
authors.lastname: Camus
authors.forename: Torsten T
authors.initials: TT
authors.lastname: Bauer
authors.forename: Ernst W
authors.initials: EW
authors.lastname: Hanisch
authors.forename: Bengt
authors.initials: B
authors.lastname: Klarin
authors.forename: Mirelle
authors.initials: M
authors.lastname: Koeman
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Krueger
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lacherade
authors.forename: Leonardo
authors.initials: L
authors.lastname: Lorente
authors.forename: Ziad A
authors.initials: ZA
authors.lastname: Memish
authors.forename: Lee E
authors.initials: LE
authors.lastname: Morrow
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Nardi
authors.forename: Christianne A
authors.initials: CA
authors.lastname: van Nieuwenhoven
authors.forename: Grant E
authors.initials: GE
authors.lastname: O'Keefe
authors.forename: George
authors.initials: G
authors.lastname: Nakos
authors.forename: Frank A
authors.initials: FA
authors.lastname: Scannapieco
authors.forename: Philippe
authors.initials: P
authors.lastname: Seguin
authors.forename: Thomas
authors.initials: T
authors.lastname: Staudinger
authors.forename: Arzu
authors.initials: A
authors.lastname: Topeli
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.forename: Marc J M
authors.initials: MJ
authors.lastname: Bonten
mesh_terms: D018806:APACHE; D016001:Confidence Intervals; D003422:Critical Care / Q000706:statistics & numerical data; D006801:Humans; D007902:Length of Stay; D053717:Pneumonia, Ventilator-Associated / Q000401:mortality*; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012720:Severity of Illness Index; D013514:Surgical Procedures, Operative / Q000706:statistics & numerical data