Received on June 5, 2008
Accepted on February 11, 2009

Proteomics and Protein Markers

Variability of N-Terminal Probrain Natriuretic Peptide in Stable Chronic Heart Failure and its Relation to Changes in Clinical Variables

¹ Department of Cardiology, Angiology Pulmonology, University of Heidelberg, Germany
² Lehrstuhl für Pharmazeutische Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
³ Roche Diagnostics, Mannheim, Germany
⁴ Roche Diagnostics, Rotkreuz, Switzerland

^* To whom correspondence should be addressed. E-mail: Lutz.Frankenstein{at}med.uni-heidelberg.de.

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.