title: Positive Predictive Value of True Bacteremia according to the Number of Positive Culture Sets in Adult Patients.
abstract: BACKGROUND
  Performing multiple blood culture sets simultaneously is a standard blood culture methodology, although it is often difficult to distinguish true bacteremia from contamination when only one of several blood culture sets is positive. This study clarified the relationship between the number of positive blood culture sets and clinical significance in patients with positive blood culture.
  
  
  METHODS
  Patients aged 18 years and over with at least 1 positive blood culture were enrolled. Positive blood culture episodes were categorized from clinical records as true bacteremia, contamination, or unknown clinical significance. The associations among episodes of true bacteremia, isolated bacteria, the number of positive blood culture sets from among the performed sets, and the clinical background of patients were analyzed.
  
  
  RESULTS
  Among a total of 407 episodes, 262, 67 and 78 were true bacteremia, contamination and unknown clinical significance, respectively. The positive predictive values (PPVs) of 1 out of 1, 1 out of 2 and 2 out of 2 positive sets in cases of Staphylococcus aureus, were 81.3%, 50% and 100% respectively; those in cases of coagulase-negative Staphylococci were 20.5%, 10.8% and 63.5%, respectively. Almost all cases of Escherichia coli, Pseudomonas aeruginosa, Klebsiella species and Candida species were true bacteremia. The probability of true bacteremia was strongly associated with recent surgery in multivariate analysis (P < 0.05).
  
  
  CONCLUSIONS
  The probability of true bacteremia based on the number of positive culture sets from among the performed sets varies by microorganism. Therefore, PPVs calculated using this method may help physicians distinguish true bacteremia from contamination.
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kitaura
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan ; †Center for Infectious diseases, Tottori University Hospital, Yonago 683-8504, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Chikumi
authors.affiliation: ‡Division of Clinical Laboratory, Tottori University Hospital, Yonago 683-8504, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Fujiwara
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Okada
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hayabuchi
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan ; †Center for Infectious diseases, Tottori University Hospital, Yonago 683-8504, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nakamoto
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Miyako
authors.initials: M
authors.lastname: Takata
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yamasaki
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Igishi
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Burioka
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Shimizu
keywords: bacteremia; blood culture; contamination; positive predictive value