title: Can we predict which patients with community-acquired pneumonia are likely to have positive blood cultures?
abstract: BACKGROUND
  Blood cultures (BC) are commonly ordered during the initial assessment of patients with community-acquired pneumonia (CAP), yet their yield remains low. Selective use of BC would allow the opportunity to save healthcare resources and avoid patient discomfort. The study was to determine what demographic and clinical factors predict a greater likelihood of a positive blood culture result in patients diagnosed with CAP.
  
  
  METHODS
  A structured retrospective systematic chart audit was performed to compare relevant demographic and clinical details of patients admitted with CAP, in whom blood culture results were positive, with those of age, sex, and date-matched control patients in whom blood culture results were negative.
  
  
  RESULTS
  On univariate analysis, eight variables were associated with a positive BC result. After logistic regression analysis, however, the only variables statistically significantly associated with a positive BC were WBC less than 4.5 × 10(9)/L [likelihood ratio (LR): 7.75, 95% CI=2.89-30.39], creatinine >106 μmol/L (LR: 3.15, 95%CI=1.71-5.80), serum glucose<6.1 mmol/L (LR: 2.46, 95%CI=1.14-5.32), and temperature > 38 °C (LR: 2.25, 95% CI =1.21-4.20). A patient with all of these variables had a LR of having a positive BC of 135.53 (95% CI=25.28-726.8) compared to patients with none of these variables.
  
  
  CONCLUSIONS
  Certain clinical variables in patients with CAP admitted to hospitals do appear to be associated with a higher probability of a positive yield of BC, with combinations of these variables increasing this likelihood. We have identified a subgroup of CAP patients in whom blood cultures are more likely to be useful.
authors.affiliation: Department of Emergency Medicine, Charles V Keating Emergency and Trauma Centre, 1796 Summer St, Halifax, Nova Scotia B3H3A7, Canada (Campbell SG, Urquhart DG) T2127 Firestone Institute for Respiratory Health, St. Joseph's Health Care Hamilton, Hamilton, ON. L8N 4A6, Canada (McIvor RA) Foothills Medical Centre, 1403 - 29th Street, N.W., University of Calgary, Calgary, Alberta, Canada (Joanis V).
authors.forename: Samuel George
authors.initials: SG
authors.lastname: Campbell
authors.affiliation: Department of Emergency Medicine, Charles V Keating Emergency and Trauma Centre, 1796 Summer St, Halifax, Nova Scotia B3H3A7, Canada (Campbell SG, Urquhart DG) T2127 Firestone Institute for Respiratory Health, St. Joseph's Health Care Hamilton, Hamilton, ON. L8N 4A6, Canada (McIvor RA) Foothills Medical Centre, 1403 - 29th Street, N.W., University of Calgary, Calgary, Alberta, Canada (Joanis V).
authors.forename: R Andrew
authors.initials: RA
authors.lastname: McIvor
authors.affiliation: Department of Emergency Medicine, Charles V Keating Emergency and Trauma Centre, 1796 Summer St, Halifax, Nova Scotia B3H3A7, Canada (Campbell SG, Urquhart DG) T2127 Firestone Institute for Respiratory Health, St. Joseph's Health Care Hamilton, Hamilton, ON. L8N 4A6, Canada (McIvor RA) Foothills Medical Centre, 1403 - 29th Street, N.W., University of Calgary, Calgary, Alberta, Canada (Joanis V).
authors.forename: Vincent
authors.initials: V
authors.lastname: Joanis
authors.affiliation: Department of Emergency Medicine, Charles V Keating Emergency and Trauma Centre, 1796 Summer St, Halifax, Nova Scotia B3H3A7, Canada (Campbell SG, Urquhart DG) T2127 Firestone Institute for Respiratory Health, St. Joseph's Health Care Hamilton, Hamilton, ON. L8N 4A6, Canada (McIvor RA) Foothills Medical Centre, 1403 - 29th Street, N.W., University of Calgary, Calgary, Alberta, Canada (Joanis V).
authors.forename: David Graydon
authors.initials: DG
authors.lastname: Urquhart
keywords: Blood cultures; Community-acquired pneumonia