BRAIN NATRIURETIC PEPTIDE IS STABLE IN WHOLE-BLOOD AND CAN BE MEASURED USING A SIMPLE RAPID ASSAY - IMPLICATIONS FOR CLINICAL-PRACTICE

Objectives-To compare the stability of brain natriuretic peptide (BNP) to that of N-terminal atrial natriuretic peptide (NT-ANP) in whole bl ood and plasma stored under different conditions. To compare a rapid, simple, direct (unextracted) BNP assay to a conventional assay using p lasma extraction. Design-Blinded, prospective, comparative study. Sett ing-Tertiary referral cardiology department. Subjects-Forty two subjec ts (24 men, 18 women) comprising 28 patients with left ventricular sys tolic dysfunction (LVSD) ranging from mild to severe and 14 healthy vo lunteers. Main outcome measures-Stability of NT-ANP and BNP when store d as whole blood or plasma at room temperature over three days. Reprod ucibility of measurements.Results-BNP was stable in whole blood stored at room temperature for three days; mean change in concentration -7.4 % (95% CI 0.6 to -14.8), (direct), -6.3% (5.0 to -16.4), (extracted); whereas a significant decline in BNP concentration was noted in plasma stored at room temperature; -23.2% (-13.7 to -31.6), (direct); -14.4% (extracted). By nonsignificant rise in NT-ANP concentration was noted both in whole blood and plasma stored at room temperature for three d ays; whole blood +8.6% (+22.3 to -3.5), plasma +6.3%, (23.2 to -8.4). The reproducibility of the BNP measurements, and particularly the rapi d, direct, measurement, was superior to that for NT-ANP. Conclusions-B NP is shown to be stable in whole blood for three days and can be meas ured using a rapid, simple assay. Routine assay of BNP is feasible in ordinary clinical practice and may be of value to general practitioner s and hospital based physicians in the diagnosis and management of pat ients with LVSD. Samples can be sent to a central laboratory without s pecial handling requirements.