title: Procalcitonin as a biomarker in equine chronic pneumopathies.
abstract: BACKGROUND
  Procalcitonin (PCT), a precursor protein of the hormone calcitonin, is a sensitive inflammatory marker in human medicine, which is primarily used for diagnosis of bacterial sepsis, but is also useful in diagnosis of exacerbation of asthma and COPD. In this study, PCT was evaluated as a potential biomarker for different chronic pneumopathies in the horse using an equine specific ELISA in comparison to established clinical markers and different interleukins. Sixty-four horses were classified as free of respiratory disease, recurrent airway obstruction (RAO), inflammatory airway disease (IAD) or chronic interstitial pneumopathy (CIP) using a scoring system. PCT concentrations were measured in plasma (n = 17) and in the cell-free supernatant of bronchoalveolar lavage (n = 64). PCT concentrations were correlated to interleukins IL-1ß and IL-6 in BALF, clinical findings and BALF cytology.
  
  
  RESULTS
  The median PCT concentrations in plasma were increased in respiratory disease (174.46 ng/ml, n = 7) compared to controls (13.94 ng/ml, n = 10, P = 0.05) and correlated to PCT in BALF supernatant (rs = 0.48). Compared to controls (5.49 ng/ml, n = 15), median PCT concentrations in BALF supernatant correlated to the overall clinical score (rs = 0.32, P = 0.007) and were significantly increased in RAO (13.40 ng/ml, n = 21) and IAD (16.89 ng/ml, n = 16), while no differences were found for CIP (12.02 ng/ml, n = 12). No significant increases were found for IL-1 and IL-6 between controls and respiratory disease in general as well as different disease groups.
  
  
  CONCLUSIONS
  Although some correlations were found between PCT in plasma, BALF supernatant and clinical scores, PCT in BALF does not seem to be a superior marker compared to established clinical markers. PCT in plasma seems to be more promising and a greater number of samples should be evaluated in further studies.
authors.affiliation: Equine Clinic, Freie Universitaet Berlin, Oertzenweg 19b, 10163, Berlin, Germany. Ann-Kristin.Barton@fu-berlin.de.
authors.forename: Ann Kristin
authors.identifier: http://orcid.org/0000-0002-3333-9647
authors.initials: AK
authors.lastname: Barton
authors.affiliation: Equine Clinic, Freie Universitaet Berlin, Oertzenweg 19b, 10163, Berlin, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Pelli
authors.affiliation: Research unit microbe-plant interactions, Helmholtz Zentrum Muenchen, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rieger
authors.affiliation: Equine Clinic, Freie Universitaet Berlin, Oertzenweg 19b, 10163, Berlin, Germany.
authors.forename: Heidrun
authors.initials: H
authors.lastname: Gehlen
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006734:Horse Diseases / Q000097:blood / Q000378:metabolism*; D006736:Horses; D053583:Interleukin-1beta / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D011498:Protein Precursors / Q000097:blood / Q000378:metabolism*; D012140:Respiratory Tract Diseases / Q000097:blood / Q000378:metabolism / Q000662:veterinary*
chemical_list: D015415:Biomarkers; D053583:Interleukin-1beta; D015850:Interleukin-6; D011498:Protein Precursors; D002116:Calcitonin
keywords: Biomarker; Chronic interstitial pneumopathy; Horse; Inflammatory airway disease; Procalcitonin; Recurrent airway obstruction