© 2007 European Society of Cardiology
Methodical approach to collecting and preserving plasma samples containing B-type natriuretic peptide
ítecká
Ist Department of Internal Medicine, University Hospital Faculty of Medicine in Hradec Kralove, Charles University in Prague, Czech Republic
Faculty of Military Health Sciences University of Defence in Hradec Kralove, Czech Republic
* Corresponding author. Ist Department of Internal Medicine, University Hospital, Sokolska 581, 500 05 Hradec Kralove, Czech Republic. Tel.: +420 495833249; fax: +420 495832006. E-mail address: pleskot{at}fnhk.cz
Received September 27, 2006; Sir,
We read with interest the recently published article by Pitzalis et al., on brain natriuretic peptide (BNP) measurement in patients receiving cardiac resynchronization therapy [1]. Although we believe that the study gave valuable findings, several limitations to the collection, handling and storage of plasma samples containing BNP exist.
1) Steady state
It is widely known that the time to reach the steady-state condition is determined by the biological half-life (3-5 half-lives) [2]. Human BNP is a 32-amino acid biologically active hormone with a half-life of 20-22 min [3,4]. Accordingly, in the case of BNP we can expect the steady state not sooner than 60-100 min. There is no doubt, that performing blood collection at the steady state is mandatory [5]. Despite this, the sampling method reported by Pitzalis and colleagues ("Blood samples were taken after the patient had been resting in a supine position for at least 30 min.") is unsatisfactory to achieve the steady state of BNP. In addition, other exogenous influences besides posture and physical activity may potentially affect variation of BNP plasma levels and make the accurate interpretation of BNP findings difficult, if not impossible [5-7].
2) Stabilizing agents
While neutral endopeptidases (NEPs) participate in BNP inactivation in vivo, after blood sample collection the main mechanism of BNP degradation in vitro is not due to NEPs [8]. In addition, it has been proved that EDTA, a metal-chelating agent which deactivates NEPs, does not inhibit BNP degradation [8]. Similarly, aprotinin is an ineffective inhibitor of BNP degradation [8]. On the other hand, other protease inhibitors such as kallikrein-specific inhibitors, e.g. D-Phe-Phe-Arg-chloromethylketone (PRACK II), have been manifested as effective inhibitors of BNP degradation in vitro [8]. For this reason, combination of EDTA and aprotinin for stabilizing BNP in blood samples as used by Pitzalis and colleagues seems to be pointless.
3) Time to analysis
The time to analysis of BNP plasma levels after blood collection is the next very important factor associated with stability of BNP [9-11]. Although it is obvious, that BNP plasma levels were not measured immediately after blood collection, Pitzalis and colleagues do not specify this delay.
We conclude, only precise and evidence based collection and storage of blood samples may lead to representative, not misleading, results for BNP plasma concentrations [12]. Research project MZO 00179906.
 |
References |
|---|
 Top References |
|---|
- Pitzalis M.V., Iacoviello M., Di Serio F., et al. Prognostic value of brain natriuretic peptide in the management of patients receiving cardiac resynchronization therapy. Eur J Heart Fail (2006) 8:509–514.
[Abstract/Free Full Text] - Birkett D.J. Pharmacokinetics made easy 11 designing dose regimens. Aust Prescr (1996) 19:76–78.
- Smith M.W., Espiner E.A., Yandle T.G., Charles C.J., Richards A.M. Delayed metabolism of human brain natriuretic peptide reflects resistance to neutral endopeptidase. J Endocrinol (2000) 167:239–246.[Abstract]
- Holmes S.J., Espiner E.A., Richards A.M., Yandle T.G., Frampton C. Renal, endocrine, and hemodynamic effects of human brain natriuretic peptide in normal man. J Clin Endocrinol Metab (1993) 76:91–96.[Abstract]
- Fraser C.G. Inherent biological variation and reference values. Clin Chem Lab Med (2004) 42:758–764.[CrossRef][Web of Science][Medline]
- Wu H.B., Smith A., Wieczorek S., et al. Biological variation for N-terminal pro- and B-type natriuretic peptides and implications for therapeutic monitoring of patients with congestive heart failure. Am J Cardiol (2003) 92:628–631.[CrossRef][Web of Science][Medline]
- Bruins S., Fokkema R., Römer J.W.P., et al. High intraindividual variation of B-type natriuretic peptide (BNP) and amino-terminal proBNP in patients with stable chronic heart failure. Clin Chem (2004) 50:2052–2058.
[Abstract/Free Full Text] - Belenky A., Smith A., Zhang B., et al. The effect of class-specific protease inhibitors on the stabilization of B-type natriuretic peptide in human plasma. Clin Chim Acta (2004) 340:163–172.[CrossRef][Web of Science][Medline]
- Mueller T., Gegenhuber A., Dieplinger B., Poelz W., Haltmayer M. Long term stability of endogenous B-type natriuretic peptide (BNP) and amino terminal proBNP (NT-proBNP) in frozen plasma samples. Clin Chem Lab Med (2004) 42(8):942–944.[CrossRef][Web of Science][Medline]
- Murdoch D.R., Byrne J., Morton J.J., et al. Brain natriuretic peptide is stable in whole blood and can be measured using a simple rapid assay: implications for clinical practice. Heart (1997) 78:594–597.
[Abstract/Free Full Text] - Buckley M.G., Marcus N.J., Yacoub M.H., Singer R.J. Prolonged stability of brain natriuretic peptide: importance for non-invasive assessment of cardiac function in clinical practice. Clin Sci (1998) 95:235–239.[CrossRef][Web of Science][Medline]
- Hazukova R., Vojacek J., Pleskot M., et al. B-type natriuretic peptide and temporary right ventricular pacing in chronic biventricular pacing. J Heart Dis (2005) 4:131. [Abstract].
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||