title: Utility of serum procalcitonin values in patients with acute exacerbations of chronic obstructive pulmonary disease: a cautionary note.
abstract: BACKGROUND
  Serum procalcitonin levels have been used as a biomarker of invasive bacterial infection and recently have been advocated to guide antibiotic therapy in patients with chronic obstructive pulmonary disease (COPD). However, rigorous studies correlating procalcitonin levels with microbiologic data are lacking. Acute exacerbations of COPD (AECOPD) have been linked to viral and bacterial infection as well as noninfectious causes. Therefore, we evaluated procalcitonin as a predictor of viral versus bacterial infection in patients hospitalized with AECOPD with and without evidence of pneumonia.
  
  
  METHODS
  Adults hospitalized during the winter with symptoms consistent with AECOPD underwent extensive testing for viral, bacterial, and atypical pathogens. Serum procalcitonin levels were measured on day 1 (admission), day 2, and at one month. Clinical and laboratory features of subjects with viral and bacterial diagnoses were compared.
  
  
  RESULTS
  In total, 224 subjects with COPD were admitted for 240 respiratory illnesses. Of these, 56 had pneumonia and 184 had AECOPD alone. A microbiologic diagnosis was made in 76 (56%) of 134 illnesses with reliable bacteriology (26 viral infection, 29 bacterial infection, and 21 mixed viral bacterial infection). Mean procalcitonin levels were significantly higher in patients with pneumonia compared with AECOPD. However, discrimination between viral and bacterial infection using a 0.25 ng/mL threshold for bacterial infection in patients with AECOPD was poor.
  
  
  CONCLUSIONS
  Procalcitonin is useful in COPD patients for alerting clinicians to invasive bacterial infections such as pneumonia but it does not distinguish bacterial from viral and noninfectious causes of AECOPD.
authors.affiliation: Department of Medicine, University of Rochester, Rochester, NY, USA. ann.falsey@rochestergeneral.org
authors.forename: Ann R
authors.initials: AR
authors.lastname: Falsey
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Becker
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Swinburne
authors.forename: Eric S
authors.initials: ES
authors.lastname: Nylen
authors.forename: Richard H
authors.initials: RH
authors.lastname: Snider
authors.forename: Maria A
authors.initials: MA
authors.lastname: Formica
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Hennessey
authors.forename: Mary M
authors.initials: MM
authors.lastname: Criddle
authors.forename: Derick R
authors.initials: DR
authors.lastname: Peterson
authors.forename: Edward E
authors.initials: EE
authors.lastname: Walsh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D015415:Biomarkers / Q000097:blood; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003937:Diagnosis, Differential; D018450:Disease Progression; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009518:New York; D011014:Pneumonia / Q000097:blood / Q000175:diagnosis* / Q000821:virology; D018410:Pneumonia, Bacterial / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D011237:Predictive Value of Tests; D011498:Protein Precursors / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology / Q000821:virology; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D015854:Up-Regulation; D014777:Virus Diseases / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide