NT-proBNP (N-terminal pro–B-type natriuretic peptide) is a protein that may serve as a biomarker for cardiovascular disease in veterinary patients and may be secreted systemically as a part of the neuroendocrine response to cardiac disease. However, stability of storage and accuracy of measurement are important concerns because of the volatile and labile nature of such peptides. This study assessed the effects of time and temperature (both freezing and room temperature). Dogs with heart disease (n = 36) and healthy dogs (n = 10) were included in the study. Serum NT-proBNP samples were drawn and were measured within 1 hour of collection. All samples were frozen at −20° C; the assay was repeated at 1, 24, 48, 72, and 96 hours after samples were thawed. The median NT-proBNP concentrations significantly increased after freezing and decreased at all time points after thawing. Results suggested that serum NT-proBNP increased and stabilized with freezing and that storage at room temperature caused concentrations to wane, particularly over time.

Commentary: This cardiac biomarker can help the veterinary clinician diagnose veterinary cardiac disease and differentiate between primary cardiac disease and respiratory disease. This study suggested that samples should be frozen to keep the peptide stable, and samples should remain frozen as long as possible before assay.

Effects of sample handling on serum N-terminal pro–B-type natriuretic peptide concentration in normal dogs and dogs with heart disease. Collins SA, Patteson MW, Connolly DJ, et al. J VET CARDIOL 12:41-48, 2010.