title: Two-year stability of NT-proBNP in frozen samples using the Roche Elecsys system.
abstract: BACKGROUND
  The in vitro stability of N-terminal (NT)-proBNP (brain natriuretic peptide) at room temperature and at 4 degrees C is excellent and has been well studied. However, less is known concerning its stability after a long-term frozen storage. This notion could be of major interest in the context of clinical evaluations.
  
  
  METHODS
  NT-proBNP was measured on 97 heparinized samples before and after a two-year frozen storage (-20 degrees C) using the Roche Elecsys system.
  
  
  RESULTS
  There is a slight but significant decrease of NT-proBNP concentration after frozen storage. However, this decrease is <10% for more than 90% of the samples and the maximum decrease is 16%. Moreover, values on frozen samples are well correlated with values on fresh samples (r = 0.99) using the following equation: NT-proBNP(stored sample) = 0.93 NT-proBNP(fresh sample) + 81. A similar equation was found in lower concentrations (NT-proBNP < or = 2000 ng/L).
  
  
  CONCLUSIONS
  These data show that NT-proBNP can be stored for at least two years at -20 degrees C before measurement without a substantial loss of immunoreactivity.
authors.affiliation: Laboratoire de Biochimie Médicale, CHU de Rouen-Hôpital Charles Nicolle, 76031 Rouen-Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Cauliez
authors.forename: J
authors.initials: J
authors.lastname: Guignery
authors.forename: S
authors.initials: S
authors.lastname: Marinier
authors.forename: I
authors.initials: I
authors.lastname: Mariau
authors.forename: A
authors.initials: A
authors.lastname: Lavoinne
mesh_terms: D005615:Freezing; D006333:Heart Failure / Q000175:diagnosis; D006801:Humans; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D011309:Preservation, Biological; D013997:Time Factors
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain