title: Role of procalcitonin and C-reactive protein in differentiation of mixed bacterial infection from 2009 H1N1 viral pneumonia.
abstract: BACKGROUND
  Mixed bacterial infection is an important contributor to morbidity and mortality during influenza pandemics. We evaluated procalcitonin (PCT) and C-reactive protein (CRP) in differentiating pneumonia caused by mixed bacterial and 2009 H1N1 influenza infection from 2009 H1N1 influenza infection alone.
  
  
  METHODS
  Data were collected retrospectively over a 7-month period during the 2009 H1N1 influenza pandemic. Patients visiting emergency department and diagnosed as community-acquired pneumonia caused by 2009 H1N1 infection were included (n = 60).
  
  
  RESULTS
  Mixed bacterial and viral infection pneumonia (n = 16) had significantly higher PCT and CRP levels than pneumonia caused by 2009 H1N1 influenza alone (n = 44, P = 0·019, 0·022 respectively). The sensitivity and specificity for detection of mixed bacterial infection pneumonia was 56% and 84% for PCT > 1·5 ng/ml, and 69% and 63% for CRP > 10 mg/dl. Using PCT and CRP in combination, the sensitivity and specificity were 50% and 93%, respectively.
  
  
  CONCLUSIONS
  Procalcitonin and CRP alone and their combination had a moderate ability to detect pneumonia of mixed bacterial infection during the 2009 H1N1 pandemic. Considering high specificity, combination of low CRP and PCT result may suggest that pneumonia is unlikely to be caused by mixed bacterial infection.
authors.affiliation: Department of Emergency Medicine, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Korea.
authors.forename: Shin
authors.initials: S
authors.lastname: Ahn
authors.forename: Won Young
authors.initials: WY
authors.lastname: Kim
authors.forename: Sung-Han
authors.initials: SH
authors.lastname: Kim
authors.forename: SangBum
authors.initials: S
authors.lastname: Hong
authors.forename: Chae-Man
authors.initials: CM
authors.lastname: Lim
authors.forename: YounSuck
authors.initials: Y
authors.lastname: Koh
authors.forename: Kyung Soo
authors.initials: KS
authors.lastname: Lim
authors.forename: Won
authors.initials: W
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D002097:C-Reactive Protein / Q000032:analysis; D002116:Calcitonin / Q000097:blood; D015740:Calcitonin Gene-Related Peptide; D060085:Coinfection / Q000097:blood / Q000175:diagnosis / Q000382:microbiology / Q000821:virology; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D011024:Pneumonia, Viral / Q000097:blood / Q000175:diagnosis* / Q000821:virology; D011498:Protein Precursors / Q000097:blood; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide