title: Variability of N-terminal probrain natriuretic peptide in stable chronic heart failure and its relation to changes in clinical variables.
abstract: BACKGROUND
  We investigated the variability of N-terminal probrain natriuretic peptide (NT-proBNP) and its relation to known confounding variables in patients with stable chronic heart failure who were on a stable optimized medication regimen.
  
  
  METHODS
  At 4 sampling intervals (14-day, 1-month, 2-month, and 3-month) the results for NT-proBNP measurements and several clinical variables were measured in samples from 41 patients with chronic systolic dysfunction who met 21 prespecified criteria for stability.
  
  
  RESULTS
  Mean within-person NT-proBNP variabilities expressed as percentage CV were 17.6%, 18.9%, 15.5%, and 16.2% at 14-day, 1-month, 2-month, and 3-month follow-up, respectively, and the corresponding reference change values were 34.6%, 52.5%, 43.1%, and 45.0%, respectively. Within-person variability of NT-proBNP was not found to be associated with renal function, weight, or waist circumference. Likewise, age, sex, baseline NT-proBNP, New York Heart Association functional class, and ejection fraction did not influence variability of NT-proBNP. The index of individuality ranged from 0.07-0.15 depending on the time interval between test results.
  
  
  CONCLUSIONS
  Although other reported studies have revealed variations in the range of 80%, in this prespecified stable heart-failure population variation of NT-proBNP at 14-day, 1-month, 2-month, and 3-month follow-up was lower and was not related to renal function or weight. In view of the low index of individuality we observed, within-person variation is quite low compared to between-person variation. Consideration of these facts is important for the interpretation of clinical trials and the use of NT-proBNP in monitoring patients with heart failure.
authors.affiliation: Department of Cardiology, Angiology, and Pulmonology; University of Heidelberg, Heidelberg, Germany. Frankenstein@med.uni-heidelberg.de
authors.forename: Lutz
authors.initials: L
authors.lastname: Frankenstein
authors.forename: Andrew
authors.initials: A
authors.lastname: Remppis
authors.forename: Joerdis
authors.initials: J
authors.lastname: Frankenstein
authors.forename: Georg
authors.initials: G
authors.lastname: Hess
authors.forename: Dietmar
authors.initials: D
authors.lastname: Zdunek
authors.forename: Karen
authors.initials: K
authors.lastname: Slottje
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Katus
authors.forename: Christian
authors.initials: C
authors.lastname: Zugck
mesh_terms: D005260:Female; D006333:Heart Failure / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D020097:Natriuretic Peptide, Brain / Q000097:blood / Q000378:metabolism*; D010446:Peptide Fragments / Q000097:blood / Q000378:metabolism*; D011446:Prospective Studies
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain