title: Circulating levels of copeptin, a novel biomarker, in lower respiratory tract infections.
abstract: BACKGROUND
  Vasopressin has haemodynamic as well as osmoregulatory effects, and reflects the individual stress response. Copeptin is co-synthesized with vasopressin, directly mirroring vasopressin levels, but is more stable in plasma and serum. Both levels are increased in patients with septic shock. Lower respiratory tract infections (LRTI) are a precursor of sepsis. Thus, we investigated circulating levels and the prognostic use of copeptin for the severity and outcome in patients with LRTI.
  
  
  METHODS
  Five hundred and forty-five consecutive patients with LRTI and 50 healthy controls were evaluated. Serum copeptin levels were measured with a new chemiluminescent sandwich immunoassay.
  
  
  RESULTS
  Of the 545 patients, 373 had community-acquired pneumonia (CAP), 60 acute exacerbations of chronic obstructive pulmonary disease (COPD), 59 acute bronchitis, 13 exacerbations of asthma and 40 other final diagnoses. Copeptin levels were significantly higher in patients with LRTI as compared to controls (P < 0.001) with highest levels in patients with CAP. Copeptin levels increased with increasing severity of CAP, as classified by the pneumonia severity index (PSI) (P < 0.001). In patients who died, copeptin levels on admission were significantly higher as compared to levels in survivors [70.0 (28.8-149.0) vs. 24.3 (10.8-43.8) pmol L(-1), P < 0.001]. The area under the receiver operating curve (AUC) for survival was 0.75 for copeptin, which was significantly higher as compared to C-reactive protein (AUC 0.61, P = 0.01), leukocyte count (AUC 0.59, P = 0.01) and similar to procalcitonin (AUC 0.68, P = 0.21).
  
  
  CONCLUSIONS
  Copeptin levels are increased with increasing severity of LRTI namely in patients with CAP and unfavourable outcome. Copeptin levels, as a novel biomarker, might be a useful tool in the risk stratification of patients with LRTI.
authors.affiliation: University Hospital Basel, Switzerland. christmj@bluewin.ch
authors.forename: B
authors.initials: B
authors.lastname: Müller
authors.forename: N
authors.initials: N
authors.lastname: Morgenthaler
authors.forename: D
authors.initials: D
authors.lastname: Stolz
authors.forename: P
authors.initials: P
authors.lastname: Schuetz
authors.forename: C
authors.initials: C
authors.lastname: Müller
authors.forename: R
authors.initials: R
authors.lastname: Bingisser
authors.forename: A
authors.initials: A
authors.lastname: Bergmann
authors.forename: M
authors.initials: M
authors.lastname: Tamm
authors.forename: M
authors.initials: M
authors.lastname: Christ-Crain
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006020:Glycopeptides / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012141:Respiratory Tract Infections / Q000175:diagnosis*; D012307:Risk Factors; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D006020:Glycopeptides; C048197:copeptins