title: Adherence to an established diagnostic threshold for ventilator-associated pneumonia contributes to low false-negative rates in trauma patients.
abstract: BACKGROUND
  The diagnosis of ventilator-associated pneumonia (VAP) in our institution has followed an established diagnostic threshold (DT) of equal to or greater than 10 colony-forming units (CFU) per milliliter on bronchoalveolar lavage (BAL) based on our previous study (PS). Because mortality from VAP is related to treatment delay, some have advocated a lower DT. The purpose of the current study (CS) was to evaluate the impact of adherence to this DT for VAP on false-negative (FN) rates and mortality in trauma patients.
  
  
  METHODS
  Consecutive patients over 9 years with VAP (defined as ≥10 CFU/mL in the BAL effluent) subsequent to the PS were identified. Data regarding each BAL performed and the colony counts of each organism identified were recorded. An FN BAL result was defined as any patient who had less than 10 CFU/mL and developed VAP with the same organism up to 7 days after the previous culture. The CS was then compared with the PS.
  
  
  RESULTS
  Over 9 years, 1,679 patients underwent 3,202 BALs. Of these, 79% were male, 88% experienced blunt injury, mean age and Injury Severity Score (ISS) were 44 years and 31, respectively. Overall, there were 73 FN BAL results (2.3%) in the CS compared with 3% in the PS (p = 0.092). In those patients with 10 organisms, the FN rate was reduced (7.5% vs. 11%, p = 0.045), and mortality was unchanged (5.4% vs. 8.3%, p = 0.361) in the CS compared with the PS. The use of the threshold equal to or greater than 10 resulted in a cumulative reduction in antibiotic charges of $1.57 million.
  
  
  CONCLUSIONS
  Continued adherence to the diagnostic threshold of equal to or greater than 10 for quantitative BAL in trauma patients has maintained a low incidence of FN BALs and reduced patient charges without impacting mortality. The purported benefit of a lower threshold is not supported. In addition, the potential sequelae of increased resistant organisms, antibiotic-related complications, and costs associated with prolonged unnecessary antibiotic exposure are minimized.
  
  
  METHODS
  Prognostic study, level III.
authors.forename: John P
authors.initials: JP
authors.lastname: Sharpe
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Magnotti
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Weinberg
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Swanson
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Schroeppel
authors.forename: L Paige
authors.initials: LP
authors.lastname: Clement
authors.forename: G Christopher
authors.initials: GC
authors.lastname: Wood
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Fabian
authors.forename: Martin A
authors.initials: MA
authors.lastname: Croce
mesh_terms: D000328:Adult; D000465:Algorithms; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D018893:Bronchoalveolar Lavage; D001999:Bronchoscopy; D015169:Colony Count, Microbial; D003428:Cross Infection / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D003937:Diagnosis, Differential; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D015601:Injury Severity Score; D007362:Intensive Care Units; D007964:Leukocytosis / Q000382:microbiology; D007970:Leukopenia / Q000382:microbiology; D008297:Male; D018410:Pneumonia, Bacterial / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D011446:Prospective Studies; D013902:Radiography, Thoracic; D014193:Trauma Centers
chemical_list: D000900:Anti-Bacterial Agents