Assessment of the stability of N-terminal pro-brain natriuretic peptide invitro: implications for assessment of left ventricular dysfunction

Plasma concentrations of N-terminal pro-brain natriuretic peptide (NT-proBN P) are raised in patients with left ventricular dysfunction. Measurement of this peptide has a potential diagnostic role in the identification and ass essment of patients with heart failure. The stability of this peptide over time periods and conditions pertaining to routine clinical practice has not been reported previously. Blood samples were obtained from 15 subjects. On e aliquot was processed immediately, and the remaining portions of the bloo d samples were stored for 24 h or 48 h at room temperature or on ice prior to processing. Plasma concentrations of NT-proBNP were measured with a nove l immunoluminometric assay developed within our laboratory. Mean plasma con centrations of NT-proBNP were nob significantly different whether blood sam ples were centrifuged immediately and stored at -70 degrees C or kept at ro om temperature or on ice for 24 h or 48 h. The mean percentage differences from baseline (reference standard) were +5.2% (95% confidence interval +18. 2 to -7.8%) and -0.8% (+15.2 to -13.7%) after storage for 24 h at room temp erature or on ice respectively, and + 8.9% (+24.2 to -6.5%) and +3.2% (+15. 1 to -0.9%) for storage for 48 h at room temperature or on ice respectively . Pearson correlation coefficients for baseline NT-proBNP concentrations co mpared with levels at 48 h at room temperature or on ice were r = 0.89 and r = 0.83 respectively (both P < 0.0001). Thus NT-proBNP extracted from plas ma samples treated with EDTA and aprotinin is stable under conditions relev ant to clinical practice.