title: Procalcitonin reflects bacteremia and bacterial load in urosepsis syndrome: a prospective observational study.
abstract: BACKGROUND
  Guidelines recommend that two blood cultures be performed in patients with febrile urinary tract infection (UTI), to detect bacteremia and help diagnose urosepsis. The usefulness and cost-effectiveness of this practice have been criticized. This study aimed to evaluate clinical characteristics and the biomarker procalcitonin (PCT) as an aid in predicting bacteremia.
  
  
  METHODS
  A prospective observational multicenter cohort study included consecutive adults with febrile UTI in 35 primary care units and 8 emergency departments of 7 regional hospitals. Clinical and microbiological data were collected and PCT and time to positivity (TTP) of blood culture were measured.
  
  
  RESULTS
  Of 581 evaluable patients, 136 (23%) had bacteremia. The median age was 66 years (interquartile range 46 to 78 years) and 219 (38%) were male. We evaluated three different models: a clinical model including seven bed-side characteristics, the clinical model plus PCT, and a PCT only model. The diagnostic abilities of these models as reflected by area under the curve of the receiver operating characteristic were 0.71 (95% confidence interval (CI): 0.66 to 0.76), 0.79 (95% CI: 0.75 to 0.83) and 0.73 (95% CI: 0.68 to 0.77) respectively. Calculating corresponding sensitivity and specificity for the presence of bacteremia after each step of adding a significant predictor in the model yielded that the PCT > 0.25 μg/l only model had the best diagnostic performance (sensitivity 0.95; 95% CI: 0.89 to 0.98, specificity 0.50; 95% CI: 0.46 to 0.55). Using PCT as a single decision tool, this would result in 40% fewer blood cultures being taken, while still identifying 94 to 99% of patients with bacteremia.The TTP of E. coli positive blood cultures was linearly correlated with the PCT log value; the higher the PCT the shorter the TTP (R(2) = 0.278, P = 0.007).
  
  
  CONCLUSIONS
  PCT accurately predicts the presence of bacteremia and bacterial load in patients with febrile UTI. This may be a helpful biomarker to limit use of blood culture resources.
authors.affiliation: Department of Infectious Diseases, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands. c.van_nieuwkoop@lumc.nl
authors.forename: Cees
authors.initials: C
authors.lastname: van Nieuwkoop
authors.forename: Tobias N
authors.initials: TN
authors.lastname: Bonten
authors.forename: Jan W
authors.initials: JW
authors.lastname: van't Wout
authors.forename: Ed J
authors.initials: EJ
authors.lastname: Kuijper
authors.forename: Geert H
authors.initials: GH
authors.lastname: Groeneveld
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Becker
authors.forename: Ted
authors.initials: T
authors.lastname: Koster
authors.forename: G Hanke
authors.initials: GH
authors.lastname: Wattel-Louis
authors.forename: Nathalie M
authors.initials: NM
authors.lastname: Delfos
authors.forename: Hans C
authors.initials: HC
authors.lastname: Ablij
authors.forename: Eliane M S
authors.initials: EM
authors.lastname: Leyten
authors.forename: Jaap T
authors.initials: JT
authors.lastname: van Dissel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000097:blood* / Q000175:diagnosis / Q000382:microbiology; D058491:Bacterial Load; D015415:Biomarkers / Q000097:blood; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D015331:Cohort Studies; D005260:Female; D005334:Fever / Q000097:blood / Q000175:diagnosis / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood*; D018805:Sepsis / Q000097:blood* / Q000175:diagnosis / Q000382:microbiology; D013577:Syndrome; D014552:Urinary Tract Infections / Q000097:blood* / Q000175:diagnosis / Q000382:microbiology
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide