title: Subthreshold quantitative bronchoalveolar lavage: clinical and therapeutic implications.
abstract: BACKGROUND
  Quantitative bronchoalveolar lavage (qBAL) is used for accurate diagnosis of ventilator-associated pneumonia (VAP). The current study aims at defining the incidence, outcomes and therapeutic implications of false-negative (FN) qBAL.
  
  
  METHODS
  Ventilated trauma, surgery, and burn, patients suspected of VAP underwent bronchoscopic qBAL. VAP was defined as qBAL with >10(5) CFU/mL (threshold). To identify FN BALs, blood cultures drawn concomitant with BAL (+/-5 days of BAL) were analyzed. qBAL specimens growing <10(5) CFU/mL (subthreshold) with blood culture identifying the same organism, without any other source, were classified as FN.
  
  
  RESULTS
  Over 39 months, 246 patients underwent 365 qBALs. Ninety-one specimens had no growth and 274 specimens grew 433 organisms--100 at threshold and 333 at subthreshold strength. Sixteen percent of threshold and 11% of subthreshold organisms were associated with bacteremia. Rates of bacteremia were similar across strengths of growth. Bacteremia at all strengths of growth was more common with Staphylococcal species (methicillin sensitive and resistant) and for hospital-acquired gram-negatives. Rates of bacteremia at all strengths of growth were significantly higher after the first week of hospitalization. Bacteremia worsened outcomes in both threshold group (higher mortality, p < 0.05) and subthreshold group (longer lengths of stay, p < 0.05).
  
  
  CONCLUSIONS
  qBAL has 11% FN rate as measured by blood stream invasion. Propensity of blood stream invasion is related to species of organism (Staphylococcal species and hospital-acquired gram-negatives) and duration of hospitalization, but not to strength of growth. Isolation of these organisms in BAL, at any strength, after the first week should prompt strong consideration for antimicrobial therapy.
authors.affiliation: Department of Surgery, Division of Trauma/Critical Care/Emergency General Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA. akmalhot@vcu.edu
authors.forename: Ajai K
authors.initials: AK
authors.lastname: Malhotra
authors.forename: Omer J
authors.initials: OJ
authors.lastname: Riaz
authors.forename: Therese M
authors.initials: TM
authors.lastname: Duane
authors.forename: Michel B
authors.initials: MB
authors.lastname: Aboutanos
authors.forename: Aaron E
authors.initials: AE
authors.lastname: Goldberg
authors.forename: Karen M
authors.initials: KM
authors.lastname: Smalara
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Borchers
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Martin
authors.forename: Rao R
authors.initials: RR
authors.lastname: Ivatury
mesh_terms: D000328:Adult; D000368:Aged; D018893:Bronchoalveolar Lavage; D001999:Bronchoscopy; D003422:Critical Care; D016208:Databases, Factual; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000175:diagnosis* / Q000382:microbiology / Q000401:mortality; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000382:microbiology / Q000401:mortality; D011237:Predictive Value of Tests; D012189:Retrospective Studies