title: C-reactive protein correlates with bacterial load and appropriate antibiotic therapy in suspected ventilator-associated pneumonia.
abstract: OBJECTIVE
  Appropriateness of antibiotic therapy is associated with reduction of bacterial load in ventilator-associated pneumonia. C-reactive protein is a valid biochemical surrogate. The objective was to determine the correlation of bacterial load, measured by quantitative tracheal aspirate (QTA), with serum C-reactive protein as an indicator of inflammatory response in episodes of ventilator-associated pneumonia and association of its variation with antibiotic appropriateness.
  
  
  METHODS
  Prospective, observational cohort study.
  
  
  METHODS
  Two medical-surgical intensive care units at large urban hospitals affiliated with teaching institutions.
  
  
  METHODS
  Sixty-eight intubated patients with monomicrobial ventilator-associated pneumonia.
  
  
  METHODS
  None.
  
  
  RESULTS
  QTA and serum C-reactive protein were measured in patients with suspected ventilator-associated pneumonia on diagnosis (baseline) and 96 hrs afterward (follow-up). Its logarithm value (logQTA) was calculated. LogQTA correlated positively with serum C-reactive protein (rho = 0.46, p < .05), temperature (rho = 0.20, p = .05), and white blood cell count (rho = 0.22, p < .05). LogQTA decreased significantly more from baseline to follow-up in patients receiving appropriate empirical antibiotic therapy compared with those with inappropriate treatment (logQTA ratio 0.77 +/- 0.22 vs. 1.02 +/- 0.27, p < .05). Mean serum C-reactive protein levels showed a similar pattern, decreasing from baseline to follow-up in patients receiving appropriate empirical antibiotic treatment but not in episodes with inappropriate treatment (C-reactive protein ratio 0.58 +/- 0.32 vs. 1.36 +/- 1.11, p < .05). There was a positive correlation between serum C-reactive protein and logQTA variations (r2 = .59, p < .05). Adjusted mean serum C-reactive protein levels by analysis of covariance on follow-up were significantly lower in patients with appropriate antibiotic treatment than in those with inappropriate empirical treatment (103 +/- 10 mg/L vs. 192 +/- 14 mg/L, p < .05). A C-reactive protein ratio of 0.8 at 96 hrs was a useful indicator of appropriateness of antibiotic therapy (sensitivity 77%; specificity 87%; area under the receiver operating characteristic curve 0.86 [0.75-0.96]).
  
  
  CONCLUSIONS
  C-reactive protein is a useful biochemical surrogate of bacterial burden in patients with ventilator-associated pneumonia. Follow-up measurements of serum C-reactive protein anticipate the appropriateness of antibiotic therapy.
authors.affiliation: Critical Care Department, Joan XXIII University Hospital, University Rovira & Virgili, Institut Pere Virgili, CIBER Enfermedades Respiratorias, Tarragona, Spain.
authors.forename: Thiago
authors.initials: T
authors.lastname: Lisboa
authors.forename: Renato
authors.initials: R
authors.lastname: Seligman
authors.forename: Emili
authors.initials: E
authors.lastname: Diaz
authors.forename: Alejandro
authors.initials: A
authors.lastname: Rodriguez
authors.forename: Paulo J Z
authors.initials: PJ
authors.lastname: Teixeira
authors.forename: Jordi
authors.initials: J
authors.lastname: Rello
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D015331:Cohort Studies; D015169:Colony Count, Microbial; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053717:Pneumonia, Ventilator-Associated / Q000097:blood* / Q000188:drug therapy* / Q000382:microbiology; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014132:Trachea / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D002097:C-Reactive Protein