Review Article
The Biologic Variability of B-Type Natriuretic Peptide and N-Terminal Pro-B-Type Natriuretic Peptide in Stable Heart Failure Patients

https://doi.org/10.1016/j.cardfail.2006.09.003Get rights and content

Abstract

Background

There are conflicting data on the usefulness of B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) in the optimization of therapy for heart failure (HF). Discordant results may be explained by the intra-individual variability of these peptides. This study evaluates the intraindividual variability of BNP and NT-proBNP and the impact of the covariates of age, sex, and renal function.

Methods and Results

Stable HF patients attending our unit were included. Blood samples were drawn 1 hour apart on 2 occasions 1 week apart. Forty-five patients were enrolled (69.6 ± 12.1 years, 64% male, 84% systolic HF). Within-hour and within-week intraindividual variability were: 6.9% and 21.1% for NT-proBNP; 14.6% and 28.4% for BNP (P < .01 for within-hour comparison of BNP and NT-proBNP). Reference change values over 1 week for NT-proBNP and BNP were 49.2% and 66.2%, respectively. There were no significant relationships identified between variability and age, gender, or glomerular filtration rate.

Conclusion

There is considerable intraindividual variability in these peptides in stable HF patients. Changes of approximately 50% and 66% for NT-proBNP and BNP from week to week are needed to indicate an altered clinical status and caution should be exercised in interpreting serial changes in these peptide levels when monitoring patient responses to treatment or clinical status.

Section snippets

Design

This was a single-center study, approved by the medical ethics committee of St. Vincent's University Hospital and fulfilled the conditions of the Declaration of Helsinki. Patients were recruited from St. Vincent's University Hospital Heart Failure Unit. Informed consent was obtained from all patients.

Patient Population

Consecutive consenting heart failure patients reviewed at the unit over a 3-month period and deemed clinically stable by the attending physician were invited to participate in the study. Clinical

Results

Forty-five patients were enrolled in this study. The baseline demographics for this population are presented in Table 1. This sample is representative of a community-based heart failure population (69.6 ± 12.1 years, 64% male, 84% systolic heart failure, 62% ischemic etiology).

There was no symptomatic change, change in volume status, or medications (cardiac and noncardiac) between Week 1 and Week 2. Creatinine and body weight measurements were also similar (Week 1 versus Week 2: 167.0 ± 196.7

Discussion

The results of this study provide further insight into the usefulness of BNP in the management of heart failure. In contrast to the group means in which no significant differences were observed, the data demonstrate sizable intraindividual variability in clinically stable patients. This is evident both within 1 hour and in samples taken 1 week apart. The difference over 1 week is particularly large, with RCV values of 49.2 and 66.2% for NT-proBNP and BNP, respectively. This variability was as

Conclusions

Although analytic variability of BNP is greater than NT-proBNP, both assays have high biologic variability, which increases with time. This study suggests that changes approximating 50% and 66% for NT-proBNP and BNP, respectively, are needed to support a clinical suspicion of change in status over 1 week. Natriuretic peptides have a well-defined role as rule-out tests, in which differences in analytic variability may not be critical. However, further research is warranted to understand this

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