title: Procalcitonin vs C-reactive protein as predictive markers of response to antibiotic therapy in acute exacerbations of COPD.
abstract: BACKGROUND
  Rational prescription of antibiotics in acute exacerbations of COPD (AECOPD) requires predictive markers. We aimed to analyze whether markers of systemic inflammation can predict response to antibiotics in AECOPD.
  
  
  METHODS
  We used data from 243 exacerbations out of 205 patients from a placebo-controlled trial on doxycycline in addition to systemic corticosteroids for AECOPD. Clinical and microbiologic response, serum C-reactive protein (CRP) level (cutoffs 5 and 50 mg/L), and serum procalcitonin level (PCT) (cutoffs 0.1 and 0.25 μg) were assessed.
  
  
  RESULTS
  Potential bacterial pathogens were identified in the majority of exacerbations (58%). We found a modest positive correlation between PCT and CRP (r = 0.46, P < .001). The majority of patients (75%) had low PCT levels, with mostly elevated CRP levels. Although CRP levels were higher in the presence of bacteria (median, 33.0 mg/L [interquartile range, 9.75-88.25] vs 17 mg/L [interquartile range, 5.0-61.0] [P = .004]), PCT levels were similar. PCT and CRP performed similarly as markers of clinical success, and we found a clinical success rate of 90% in patients with CRP ≤ 5 mg/L. A significant effect of doxycycline was observed in patients with a PCT level < .1 μg/L (treatment effect, 18.4%; P = .003). A gradually increasing treatment effect of antibiotics (6%, 10%, and 18%), although not significant, was found for patients with CRP values of ≤ 5, 6-50, and > 50 mg/L, respectively.
  
  
  CONCLUSIONS
  Contrary to the current literature, this study suggests that patients with low PCT values do benefit from antibiotics. CRP might be a more valuable marker in these patients.
authors.affiliation: Department of Pulmonary Diseases, Medical Centre Alkmaar, The Netherlands. j.daniels@vumc.nl
authors.forename: Johannes M A
authors.initials: JM
authors.lastname: Daniels
authors.forename: Marianne
authors.initials: M
authors.lastname: Schoorl
authors.forename: Dominic
authors.initials: D
authors.lastname: Snijders
authors.forename: Dirk L
authors.initials: DL
authors.lastname: Knol
authors.forename: René
authors.initials: R
authors.lastname: Lutter
authors.forename: Henk M
authors.initials: HM
authors.lastname: Jansen
authors.forename: Wim G
authors.initials: WG
authors.lastname: Boersma
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D004318:Doxycycline / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006023:Glycoproteins; D006801:Humans; D008297:Male; D009391:Nephelometry and Turbidimetry; D011498:Protein Precursors / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology; D012008:Recurrence; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; C000606589:CALCA protein, human; D006023:Glycoproteins; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide; D004318:Doxycycline