title: [Predictive factors of contamination in a blood culture with bacterial growth in an Emergency Department].
abstract: BACKGROUND
  The aim of this study is to identify predictive factors of bacterial contamination in positive blood cultures (BC) collected in an emergency department.
  
  
  METHODS
  A prospective, observational and analytical study was conducted on febrile children aged on to 36 months, who had no risk factors of bacterial infection, and had a BC collected in the Emergency Department between November 2011 and October 2013 in which bacterial growth was detected. The potential BC contamination predicting factors analysed were: maximum temperature, time to positivity, initial Gram stain result, white blood cell count, absolute neutrophil count, band count, and C-reactive protein (CRP).
  
  
  RESULTS
  Bacteria grew in 169 BC. Thirty (17.8%) were finally considered true positives and 139 (82.2%) false positives. All potential BC contamination predicting factors analysed, except maximum temperature, showed significant differences between true positives and false positives. CRP value, time to positivity, and initial Gram stain result are the best predictors of false positives in BC. The positive predictive values of a CRP value≤30mg/L, BC time to positivity≥16h, and initial Gram stain suggestive of a contaminant in predicting a FP, are 95.1, 96.9 and 97.5%, respectively. When all 3 conditions are applied, their positive predictive value is 100%. Four (8.3%) patients with a false positive BC and discharged to home were revaluated in the Emergency Department.
  
  
  CONCLUSIONS
  The majority of BC obtained in the Emergency Department that showed positive were finally considered false positives. Initial Gram stain, time to positivity, and CRP results are valuable diagnostic tests in distinguishing between true positives and false positives in BC. The early detection of false positives will allow minimising their negative consequences.
authors.affiliation: Servicio de Urgencias, Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, España. Electronic address: shernandez@hsjdbcn.org.
authors.forename: S
authors.initials: S
authors.lastname: Hernández-Bou
authors.affiliation: Servicio de Urgencias, Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, España.
authors.forename: V
authors.initials: V
authors.lastname: Trenchs Sainz de la Maza
authors.affiliation: Servicio de Urgencias, Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, España.
authors.forename: J N
authors.initials: JN
authors.lastname: Esquivel Ojeda
authors.affiliation: Servicio de Microbiología, Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, España.
authors.forename: A
authors.initials: A
authors.lastname: Gené Giralt
authors.affiliation: Servicio de Urgencias, Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, España.
authors.forename: C
authors.initials: C
authors.lastname: Luaces Cubells
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D000071997:Blood Culture; D002675:Child, Preschool; D004636:Emergency Service, Hospital; D005260:Female; D005544:Forecasting; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies
keywords: Bacteraemia; Bacteriemia; Blood culture; Contaminación; Contamination rate; Emergency Department; Hemocultivos; Servicio de Urgencias