Predictive value of blood cultures positive for coagulase-negative staphylococci: implications for patient care and health care quality assurance

Clin Infect Dis. 2004 Aug 1;39(3):333-41. doi: 10.1086/421941. Epub 2004 Jul 12.


Interpretation of blood cultures that are positive for coagulase-negative staphylococci (CoNS) is often difficult. Predictive values for blood cultures positive for CoNS in patients with a central vascular line in place were calculated using the following rates: true bacteremia, 3%; blood culture contamination, 2%; detection of bacteremia, 80%; and catheter colonization, 2% (for blood samples obtained through a central vascular line). Positive predictive values were 55% for 1 positive culture result of 1 culture performed, 20% for 1 positive result of 2 performed, and only 5% for 1 positive result of 3 performed. For 2 positive culture results of 2 cultures performed, the positive predictive value was 98% if both samples were obtained through the vein, 96% if one sample was obtained through a catheter and the other was obtained by vein, and only 50% if both samples were obtained through a catheter. Use of this model with institution-specific values for input parameters would assist in clinical decision-making as well as hospital quality assurance.

MeSH terms

  • Bacteremia / diagnosis
  • Bacteremia / microbiology*
  • Blood / microbiology*
  • Catheters, Indwelling / microbiology
  • Coagulase / analysis
  • Equipment Contamination
  • Humans
  • Models, Statistical
  • Predictive Value of Tests
  • Staphylococcal Infections / diagnosis*
  • Staphylococcal Infections / microbiology
  • Staphylococcus / classification
  • Staphylococcus / enzymology
  • Staphylococcus / isolation & purification*


  • Coagulase