title: The effect of protease inhibition on the temporal stability of NT-proBNP in feline plasma at room temperature.
abstract: OBJECTIVE
  To evaluate whether the addition of a protease inhibitor (PI) to feline plasma improves the temporal stability of N-terminal pro-B-type natriuretic peptide (NT-proBNP).
  
  
  METHODS
  Forty-four EDTA blood samples were collected from 42 cats with cardiac disease or hyperthyroidism. Samples were separated within 15 min of collection and the plasma stored at -80 °C. Samples were thawed and each separated into 2 aliquots, one of which was mixed with PI. Each was subdivided into 5 aliquots, which remained at room temperature (RT) for zero, 24, 48, 96 or 120 h before being returned to storage at -80 °C. NT-proBNP was measured using a commercially-available ELISA.
  
  
  RESULTS
  There was no difference in NT-proBNP measurements between plain and PI samples at time zero (P = 0.836) or 24 h (P = 0.293). At subsequent time-points NT-proBNP was higher in the PI than the plain samples (P < 0.05). An overall effect of time at RT was detected for plain (P < 0.001) and PI samples (P < 0.001).
  
  
  CONCLUSIONS
  The addition of PI to feline plasma significantly reduces, but does not eliminate, degradation of NT-proBNP at RT. This degradation occurs over a time course comparable to postal transportation of samples for laboratory analysis and may alter the clinical interpretation of results.
authors.affiliation: Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, United Kingdom. dconnolly@rvc.ac.uk
authors.forename: David J
authors.initials: DJ
authors.lastname: Connolly
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Hezzell
authors.forename: Virginia Luis
authors.initials: VL
authors.lastname: Fuentes
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Chang
authors.forename: Rebecca
authors.initials: R
authors.lastname: Swan
authors.forename: Harriet M
authors.initials: HM
authors.lastname: Syme
mesh_terms: D000818:Animals; D002415:Cats / Q000097:blood*; D020097:Natriuretic Peptide, Brain / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology*; D013048:Specimen Handling; D013696:Temperature; D013997:Time Factors
chemical_list: D010446:Peptide Fragments; D011480:Protease Inhibitors; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain