Key result
Week-to-week intraindividual biological variation was high for both BNP (40%) and NT-proBNP (35%) in stable heart failure patients, yielding reference change values of 113% and 98%, respectively.
Why the study?
What is the intraindividual biological variation of BNP and NT-proBNP in patients with stable chronic heart failure?
Observational (n=43)
What is the intraindividual biological variation of BNP and NT-proBNP in patients with stable chronic heart failure?
High intraindividual variation of BNP and NT-proBNP in stable heart failure patients complicates the interpretation of serial measurements for disease monitoring and treatment optimization.
High biological variation warrants caution interpreting serial BNP/NT-proBNP changes in stable HF; leaves open optimal thresholds for monitoring.
BACKGROUND: Plasma B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are promising markers for heart failure diagnosis, prognosis, and treatment. Insufficient data on the intraindividual biological variation (CV(i)) of BNP and NT-proBNP hamper interpretation of changes in concentration on disease progression or treatment optimization. We therefore investigated CV(i) values in stable heart failure patients. METHODS: We recruited 43 patients with stable chronic heart failure living in Curacao (22 males, 21 females; median age, 63 years; range, 20-86 years; New York Heart Association classes I-III). Samples were collected for within-day CV(i) (n = 6; every 2 h starting at 0800), day-to-day CV(i) (n = 5; samples collected between 0800 and 1000 on 5 consecutive days), and week-to-week CV(i) (n = 6; samples collected between 0800 and 1000 on the same day of the week for 6 consecutive weeks). NT-proBNP (Roche) and BNP (Abbott) were measured by immunoassay. RESULTS: Median (range) concentrations were 134 (0-1630) ng/L (BNP) and 570 (17-5048) ng/L (NT-proBNP). Analytical variation, week-to-week CV(i), and reference change values were 8.4%, 40%, and 113% (BNP), and 3.0%, 35%, and 98% (NT-proBNP). Week-to week CV(i)s were inversely related to median BNP concentrations. Week-to week CV(i)s for BNP were 44% (BNP < or =350 ng/L) and 30% (BNP >350 ng/L). Both BNP and NT-proBNP increased between 0800 and 1000. Median NT-proBNP/BNP ratios were inversely related to median BNP concentrations. CONCLUSIONS: The high CV(i)s hamper interpretation of changes in BNP and NT-proBNP concentrations and may partly explain their poor diagnostic values in chronic heart failure. Easily modifiable determinants to lower CV(i) have not been identified. The value of BNP and NT-proBNP for chronic heart failure diagnosis, and especially for follow-up and treatment optimization of individuals, remains largely to be established.
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Bruins et al. (2004) conducted an observational in stable chronic heart failure (n=43). BNP and NT-proBNP measurement was evaluated on Intraindividual biological variation (CVi) of BNP and NT-proBNP. Week-to-week intraindividual biological variation was high for both BNP (40%) and NT-proBNP (35%) in stable heart failure patients, yielding reference change values of 113% and 98%, respectively.
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