title: Variation of infected cell count in bronchoalveolar lavage and timing of ventilator-associated pneumonia.
abstract: OBJECTIVE
  The aim of this study was to evaluate and compare the accuracy of the percentage of infected cells (%IC) in bronchoalveolar lavage (BAL) for ventilator-associated pneumonia (VAP) diagnosis according to its onset from the initiation of mechanical ventilation.
  
  
  METHODS
  One hundred and eight patients admitted to a surgical ICU were retrospectively included (1999-2001). A total of 171 cases of VAP were diagnosed on clinical, biological, chest X-ray and BAL results (threshold >/=10(4 )cfu/ml).
  
  
  RESULTS
  The %IC significantly decreased with the timing of VAP diagnosis: 12.2+/-12.1% for VAP occurring less than 7 days after the initiation of mechanical ventilation, 7.4+/-9.2% for VAP occurring between 7 and 15 days and 4.8+/-6.4% for VAP after 15 days ( p=0.0002), despite the same number of elements and proportion of polymorphonuclear neutrophils in BAL. In addition, a relationship between the %IC and the pathogen responsible for VAP was observed for P. aeruginosa [higher for VAP <7 days than for VAP 7-15 days ( p=0.01) and VAP >15 days ( p=0.006)] and S. aureus [lower for VAP >15 days than VAP 7-15 days ( p=0.04) and VAP <7 days ( p=0.04)]. Furthermore, the %IC in BAL was lower in patients undergoing antimicrobial therapy than in patients without antibiotics ( p=0.04). Three factors were independently associated with the %IC: quantitative culture of BAL (beta=0.42, p<0.0001), ongoing antimicrobial therapy (beta= -0.21, p=0.003) and onset of VAP (beta= -0.17, p=0.01).
  
  
  CONCLUSIONS
  A relationship between the %IC in BAL, duration of ventilation, quantitative culture of BAL and ongoing antimicrobial therapy has been proved in this study. The %IC for VAP diagnosis may not be accurate in patients with ongoing antibiotics and late onset infections (>7 days).
authors.affiliation: Réanimation Chirurgicale, Groupe Hospitalier Bichat Claude Bernard, 46 rue Henri Huchard, 75877 Paris Cedex, France. dupont.herve@chu-amiens.fr
authors.forename: Hervé
authors.initials: H
authors.lastname: Dupont
authors.forename: Viviane
authors.initials: V
authors.lastname: Chalhoub
authors.forename: Gaëtan
authors.initials: G
authors.lastname: Plantefève
authors.forename: Cyrille
authors.initials: C
authors.lastname: De Vaumas
authors.forename: Nathalie
authors.initials: N
authors.lastname: Kermarrec
authors.forename: Catherine
authors.initials: C
authors.lastname: Paugam-Burtz
authors.forename: Jean
authors.initials: J
authors.lastname: Mantz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018893:Bronchoalveolar Lavage; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology / Q000382:microbiology; D002452:Cell Count; D016009:Chi-Square Distribution; D003428:Cross Infection / Q000382:microbiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000382:microbiology*; D011237:Predictive Value of Tests; D012121:Respiration, Artificial / Q000009:adverse effects*; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D013997:Time Factors