title: Use of Transthoracic Echocardiography in the Management of Low-Risk Staphylococcus aureus Bacteremia: Results From a Retrospective Multicenter Cohort Study.
abstract: OBJECTIVE
  The aim of this study was to develop a prediction model to identify patients with low-risk Staphylococcus aureus bacteremia (SAB), in whom infective endocarditis (IE) can be ruled out based on transthoracic echocardiogram (TTE).
  
  
  BACKGROUND
  S. aureus is a major cause of bacteremia and often leads to IE. Current guidelines recommend performing transesophageal echocardiography on all patients or treating all patients empirically with prolonged intravenous antibiotics; however, this approach is resource intensive, many physicians do not adhere to guidelines, and recent studies suggest that low-risk patients may not require transesophageal echocardiography.
  
  
  METHODS
  We conducted a retrospective cohort study of 833 consecutive hospitalized patients with SAB from 7 academic and community hospitals in Toronto, Canada, over a 3-year period (2007 to 2010). Patients who received a TTE within 28 days of bacteremia (n = 536) were randomly divided into derivation and validation cohorts. Multivariable logistic regression analysis was used to determine high-risk criteria for IE in the derivation cohort, and criteria were then applied to the validation cohort to determine diagnostic properties.
  
  
  RESULTS
  Four high-risk criteria predicted IE: indeterminate or positive TTE (p < 0.001), community-acquired bacteremia (p = 0.034), intravenous drug use (p < 0.001), and high-risk cardiac condition (p < 0.004). In the validation cohort, the presence of any 1 of the high-risk criteria had 97% sensitivity (95% confidence interval [CI]: 87% to 100%) and 99% negative predictive value (95% CI: 96% to 100%) for IE. The negative likelihood ratio was 0.05 (95% CI: 0.007 to 0.35).
  
  
  CONCLUSIONS
  A normal TTE ruled out IE in patients without community-acquired SAB, high-risk cardiac conditions, and intravenous drug use. This study provides evidence that clinical risk stratification combined with a normal TTE may be adequate to rule out IE in most patients with SAB.
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada; Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Showler
authors.affiliation: Mount Sinai Hospital, Toronto, Ontario, Canada; Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Burry
authors.affiliation: Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Bai
authors.affiliation: Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Steinberg
authors.affiliation: Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada; Lakeridge Health, Oshawa, Ontario, Canada.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ricciuto
authors.affiliation: Trillium Health Partners, Mississauga, Ontario, Canada.
authors.forename: Tania
authors.initials: T
authors.lastname: Fernandes
authors.affiliation: Trillium Health Partners, Mississauga, Ontario, Canada.
authors.forename: Anna
authors.initials: A
authors.lastname: Chiu
authors.affiliation: North York General Hospital, Toronto, Ontario, Canada.
authors.forename: Sumit
authors.initials: S
authors.lastname: Raybardhan
authors.affiliation: Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Science
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eshan
authors.initials: E
authors.lastname: Fernando
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada; Mount Sinai Hospital, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Chaim M
authors.initials: CM
authors.lastname: Bell
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada; Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada; Mount Sinai Hospital, Toronto, Ontario, Canada. Electronic address: amorris@mtsinai.on.ca.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Morris
mesh_terms: D000368:Aged; D016470:Bacteremia / Q000150:complications*; D015331:Cohort Studies; D017714:Community-Acquired Infections; D004452:Echocardiography; D004696:Endocarditis / Q000175:diagnosis*; D005260:Female; D005544:Forecasting; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000150:complications*
keywords: Staphylococcus aureus; bacteremia; echocardiogram; endocarditis