title: Procalcitonin for diagnosis of bacterial pneumonia in critically ill patients during 2009 H1N1 influenza pandemic: a prospective cohort study, systematic review and individual patient data meta-analysis.
abstract: BACKGROUND
  Procalcitonin (PCT) is helpful for diagnosing bacterial infections. The diagnostic utility of PCT has not been examined thoroughly in critically ill patients with suspected H1N1 influenza.
  
  
  METHODS
  Clinical characteristics and PCT were prospectively assessed in 46 patients with pneumonia admitted to medical ICUs during the 2009 and 2010 influenza seasons. An individual patient data meta-analysis was performed by combining our data with data from five other studies on the diagnostic utility of PCT in ICU patients with suspected 2009 pandemic influenza A(H1N1) virus infection identified by performing a systematic literature search.
  
  
  RESULTS
  PCT levels, measured within 24 hours of ICU admission, were significantly elevated in patients with bacterial pneumonia (isolated or coinfection with H1N1; n = 77) (median = 6.2 μg/L, interquartile range (IQR) = 0.9 to 20) than in patients with isolated H1N1 influenza pneumonia (n = 84; median = 0.56 μg/L, IQR = 0.18 to 3.33). The area under the curve of the receiver operating characteristic curve of PCT was 0.72 (95% confidence interval (CI) = 0.64 to 0.80; P < 0.0001) for diagnosis of bacterial pneumonia, but increased to 0.76 (95% CI = 0.68 to 0.85; P < 0.0001) when patients with hospital-acquired pneumonia and immune-compromising disorders were excluded. PCT at a cut-off of 0.5 μg/L had a sensitivity (95% CI) and a negative predictive value of 80.5% (69.9 to 88.7) and 73.2% (59.7 to 84.2) for diagnosis of bacterial pneumonia, respectively, which increased to 85.5% (73.3 to 93.5) and 82.2% (68.0 to 92.0) in patients without hospital acquired pneumonia or immune-compromising disorder.
  
  
  CONCLUSIONS
  In critically ill patients with pneumonia during the influenza season, PCT is a reasonably accurate marker for detection of bacterial pneumonia, particularly in patients with community-acquired disease and without immune-compromising disorders, but it might not be sufficient as a stand-alone marker for withholding antibiotic treatment.
authors.forename: Roman
authors.initials: R
authors.lastname: Pfister
authors.forename: Matthias
authors.initials: M
authors.lastname: Kochanek
authors.forename: Timo
authors.initials: T
authors.lastname: Leygeber
authors.forename: Christian
authors.initials: C
authors.lastname: Brun-Buisson
authors.forename: Elise
authors.initials: E
authors.lastname: Cuquemelle
authors.forename: Mariana Benevides
authors.initials: MB
authors.lastname: Machado
authors.forename: Enrique
authors.initials: E
authors.lastname: Piacentini
authors.forename: Naomi E
authors.initials: NE
authors.lastname: Hammond
authors.forename: Paul R
authors.initials: PR
authors.lastname: Ingram
authors.forename: Guido
authors.initials: G
authors.lastname: Michels
mesh_terms: D000328:Adult; D000368:Aged; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D015331:Cohort Studies; D016638:Critical Illness / Q000453:epidemiology; D003428:Cross Infection / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D018410:Pneumonia, Bacterial / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood*; D012189:Retrospective Studies
chemical_list: C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide