title: Procalcitonin and C-reactive protein levels in community-acquired pneumonia: correlation with etiology and prognosis.
abstract: BACKGROUND
  The diagnostic value of admission serum levels of procalcitonin (PCT) and C-reactive protein (CRP) as indicators of the etiology and prognosis was prospectively investigated.
  
  
  METHODS
  96 patients, 50-85 years of age, treated in the hospital for community-acquired pneumonia (CAP).
  
  
  RESULTS
  On admission, all patients had elevated CRP levels (> 10 mg/l), but only 60 patients (54%) had elevated PCT levels (> 0.1 microgram/l). The severity of disease measured by APACHE II score was strongly associated with admission levels of PCT (p = 0.006), but not with CRP. Eight of nine patients with pneumonia caused by atypical agents had PCT levels < 0.5 microgram/l compared with 6/27 patients with pneumonia caused by classic bacterial pathogens, mainly Streptococcus pneumoniae (p = 0.03). No such correlation between CRP levels and etiology was found.
  
  
  CONCLUSIONS
  Our data indicate that in patients admitted to the hospital with CAP, measurement of PCT gives information about the severity of the disease, and may aid the physician to differentiate typical bacterial etiology from atypical etiology, and thereby to choose appropriate initial antibiotic treatment.
authors.affiliation: Div. of Infectious Diseases, Karolinska Institutet, Karolinska Hospital, Stockholm, Sweden. jonas.hedlund@divmed.ks.se
authors.forename: J
authors.initials: J
authors.lastname: Hedlund
authors.forename: L O
authors.initials: LO
authors.lastname: Hansson
mesh_terms: D018806:APACHE; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D017714:Community-Acquired Infections / Q000097:blood / Q000175:diagnosis / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D011018:Pneumonia, Pneumococcal / Q000097:blood / Q000175:diagnosis / Q000382:microbiology; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood*
chemical_list: C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide