title: Procalcitonin versus C-reactive protein for predicting pneumonia in adults with lower respiratory tract infection in primary care.
abstract: BACKGROUND
  The role of procalcitonin in diagnosing bacterial infection has mainly been studied in patients with severe infections. There is no study on the value of procalcitonin measurements in adults with lower respiratory tract infection (LRTI) treated in primary care.
  
  
  OBJECTIVE
  To evaluate the accuracy of plasma procalcitonin in predicting radiographic pneumonia, bacterial infection, and adverse outcome in a population of adults with LRTI treated in primary care.
  
  
  METHODS
  Prospective, observational study.
  
  
  METHODS
  Forty-two general practices and an outpatient clinic at the Department of Infectious Diseases, Odense University Hospital, Denmark.
  
  
  METHODS
  A total of 364 patients with LRTI were prospectively enrolled from 42 general practices. Patients were examined with chest radiography, microbiological analyses, and measurements of C-reactive protein (CRP) and procalcitonin. The outcome measure was hospitalisation within 4 weeks of enrollment.
  
  
  RESULTS
  Median procalcitonin was 0.05 ng/ml, which was below the functional sensitivity of the assay (0.06 ng/ml). In predicting radiographic pneumonia, bacterial infection, and hospitalisation, the sensitivities of procalcitonin >0.06 ng/ml were 0.70, 0.51, and 0.67, and of CRP were > or =20 mg/l, 0.73, 0.56, and 0.74 respectively. Corresponding positive predictive values were between 0.09 and 0.28.
  
  
  CONCLUSIONS
  Both procalcitonin >0.06 ng/ml and CRP > or =20 mg/l were associated with radiographic pneumonia, bacterial infection, and subsequent hospitalisation, but positive predictive values were too low for any of the two inflammatory markers to be of use in clinical practice. To measure procalcitonin values accurately in the primary care setting, a more sensitive method is needed, but there was no indication that procalcitonin is superior to CRP in identifying patients with pneumonia, bacterial aetiology, or adverse outcome.
authors.affiliation: Department of Infectious Diseases C, Odense University Hospital, Denmark. anette.holm@ouh.regionsyddanmark.dk
authors.forename: Anette
authors.initials: A
authors.lastname: Holm
authors.forename: Svend S
authors.initials: SS
authors.lastname: Pedersen
authors.forename: Joergen
authors.initials: J
authors.lastname: Nexoe
authors.forename: Niels
authors.initials: N
authors.lastname: Obel
authors.forename: Lars P
authors.initials: LP
authors.lastname: Nielsen
authors.forename: Ole
authors.initials: O
authors.lastname: Koldkjaer
authors.forename: Court
authors.initials: C
authors.lastname: Pedersen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000378:metabolism*; D015740:Calcitonin Gene-Related Peptide; D003718:Denmark; D005194:Family Practice; D006801:Humans; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000175:diagnosis*; D011024:Pneumonia, Viral / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011498:Protein Precursors / Q000378:metabolism*; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide