Disparity between studies of the stability of BNP in blood: comparison of endogenous and exogenous peptide.

Measurement of plasma concentrations of the natriuretic peptides has recently been recognised as a potentially useful means of identifying patients with left ventricular systolic dysfunction (LVSD). Most studies, including our own, suggest that brain natriuretic peptide (BNP) may be superior to N-terminal atrial natriuretic peptide for diagnostic purposes. The widespread applicability of BNP would, nevertheless, be greatly diminished if the blood sample required special storage or handling. We have previously shown in a mixed population—including patients with LVSD and healthy volunteers—that endogenous BNP is stable in whole blood at room temperature for three days. However, other groups have published conflicting results, which at first sight cast doubt on our data; therefore, our results have not gained universal acceptance. We, therefore, repeated our study and confirmed our original findings. Interestingly, our study is in agreement with the only other one to examine the stability of the endogenous peptide. This led us to believe that the disparity may have arisen because other groups have looked at the stability of exogenous rather than endogenous BNP. We report the results of a study directly comparing the stability of endogenous and exogenous BNP.