title: Atrial natriuretic peptide vs. N-terminal-pro-atrial natriuretic peptide for the detection of left atrial dilatation in horses.
abstract: BACKGROUND
  Studies on the use of atrial natriuretic peptide (ANP) as a biomarker for left atrial dilatation in horses have produced variable results. Few have been performed, and the results may have been influenced by ANP instability, differences in sampling protocol and changes in the assay over time. N-Terminal proANP (NT-proANP) is a more stable molecule and might be a good alternative for clinical use.
  
  
  OBJECTIVE
  To compare ANP and NT-proANP in terms of the detection of left atrial dilatation and to determine the influence of sample storage at temperatures of -80 and -20°C.
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  Atrial natriuretic peptide and NT-proANP concentrations were compared between healthy horses (Group 1, n = 20), horses with mitral valve regurgitation and a normal atrial size (Group 2, n = 11) and horses with mitral valve regurgitation associated with left atrial dilatation (Group 3, n = 16). The ANP concentration was measured with an equine enzyme-linked immunosorbent assay and the NT-proANP concentration with an enzyme-linked immunosorbent assay developed for use in human patients. Samples were stored at -20 and -80°C and analysed within 7 months.
  
  
  RESULTS
  The NT-proANP concentrations were not significantly different between the groups. Horses in Group 3 had a significantly higher ANP concentration (median 366 pg/ml; interquartile range [IQR] 74-2000 pg/ml) compared with horses in Group 1 (median 31 pg/ml; IQR 31-333 pg/ml) or Group 2 (median 31 pg/ml; IQR 31-1152 pg/ml; P = 0.02). The ANP cut-off value for detection of left atrial dilatation was 52 pg/ml (sensitivity 81%; specificity 84%) for sample storage at -80°C, and 44 pg/ml (sensitivity 69%; specificity 84%) for storage at -20°C. A larger decrease in ANP (45 ± 126 pg/ml) than in NT-proANP (10 ± 31 pg/ml) was found associated with sample storage at -20 instead of -80°C.
  
  
  CONCLUSIONS
  Atrial natriuretic peptide, but not NT-proANP, can be used to detect left atrial dilatation in horses. Atrial natriuretic peptide is less stable than NT-proANP when samples are stored at -20°C. Atrial natriuretic peptide is a more suitable biomarker of left atrial dilatation in horses than NT-proANP.
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: van der Vekens
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Decloedt
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: de Clercq
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Ven
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Sys
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: van Loon
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood*; D004108:Dilatation, Pathologic / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D005260:Female; D006331:Heart Diseases / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D006734:Horse Diseases / Q000097:blood*; D006736:Horses; D008297:Male; D011498:Protein Precursors / Q000097:blood*
chemical_list: C099254:N-terminal proatrial natriuretic peptide; D011498:Protein Precursors; D009320:Atrial Natriuretic Factor
keywords: atrial enlargement; atrial natriuretic peptides; cardiac biomarkers; horse