Effects of sample handling on serum N-terminal proB-type natriuretic peptide concentration in normal dogs and dogs with heart disease

ObjectivesTo determine whether serum N-terminal B-type natriuretic peptide (NT-proBNP) concentration in normal dogs, and dogs with heart disease, is affected by freezing, or by sample ageing when stored at room temperature.Animals, materials and methodsThirty six dogs with heart disease and ten normal dogs. Serum NT-proBNP was measured within 60 min of sample collection. Serum was also frozen at −20 °C and NT-proBNP measurement was repeated at 1, 24, 48, 72 and 96 h after thawing.ResultsMedian NT-proBNP increased significantly after freezing (p < 0.005) and then progressively decreased at all time points after thawing (p < 0.005).ConclusionsSerum NT-proBNP concentration increases with freezing, and then rapidly decreases over time when stored at room temperature. Concentrations were sufficiently increased after freezing and decreased after 24 h at room temperature to affect interpretation. The authors recommend that serum for NT-proBNP assay should be frozen within 1 h of sampling and submitted frozen in cold packs.