title: The effects of storage conditions on measurements of canine N-terminal pro-B-type natriuretic peptide.
abstract: OBJECTIVE
  The study aims were to assess the temporal stability following storage at room temperature, the effect of up to 4 freeze-thaw cycles and the effect of simulated freezer failure on measurements of canine N-terminal pro-B-type natriuretic peptide (NT-proBNP) in serum and protease-inhibited (PI) plasma.
  
  
  METHODS
  Twenty-five blood samples were collected from 16 dogs with myxomatous mitral valve disease.
  
  
  METHODS
  Aliquots of canine serum and PI plasma were stored at room temperature (17-26 °C) for 30 min, 6, 24, 48 and 72 h, respectively. Further aliquots were subjected to between 1 and 4 freeze-thaw cycles. A further aliquot was transferred to storage at 4 °C for 24 h while a paired aliquot remained at -80 °C. All samples were returned to storage at -80 °C until subsequent analysis. N-terminal pro-B-type natriuretic peptide was measured in serum and PI plasma samples using first- and second-generation versions of a commercially-available ELISA. Repeated measures models were used to assess change in NT-proBNP measurements. Wilcoxon signed ranks were used to compare paired measurements.
  
  
  RESULTS
  N-terminal pro-B-type natriuretic peptide concentrations declined over time in all samples stored at room temperature. Of the four situations tested, the rate of decrease was lowest for PI plasma samples measured using the second-generation assay. N-terminal pro-B-type natriuretic peptide is stable in samples subjected to up to 4 freeze-thaw cycles and in previously-frozen samples stored at 4 °C for 24 h.
  
  
  CONCLUSIONS
  Use of the second-generation assay, compared with the first-generation, resulted in significantly higher recovery of NT-proBNP measured in PI plasma stored at room temperature. Transport of serum at room temperature for NT-proBNP measurement is not recommended.
authors.affiliation: Department of Clinical Science and Services, The Royal Veterinary College, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, United Kingdom. Electronic address: mhezzell@vet.upenn.edu.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Hezzell
authors.affiliation: Department of Clinical Science and Services, The Royal Veterinary College, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, United Kingdom.
authors.forename: Adrian
authors.initials: A
authors.lastname: Boswood
authors.affiliation: Department of Comparative Biomedical Sciences, The Royal Veterinary College, Royal College Street, London NW1 0TU, United Kingdom.
authors.forename: Nicola
authors.initials: N
authors.lastname: Lötter
authors.affiliation: Department of Comparative Biomedical Sciences, The Royal Veterinary College, Royal College Street, London NW1 0TU, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Elliott
mesh_terms: D000818:Animals; D004285:Dogs / Q000097:blood*; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D013048:Specimen Handling / Q000662:veterinary*; D013696:Temperature; D013997:Time Factors
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain
keywords: Clinical pathology; Dog; NT-proBNP; Sample handling