Evaluation of Serum NT-proBNP Levels in Dogs with Respiratory Distress Associated with Heart disease and Respiratory Disease

The association between severity of heart disease and serum N-terminal prohormone B-type natriuretic peptide (NT-proBNP) was determined in dogs presented with respiratory distress. Four groups of dogs were divided into healthy control (n=11), heart failure (n=58), heart disease without heart failure (n=17) and respiratory disease (n=20). Serum NT-proBNP concentrations were measured with an ELISA designed for using in dogs. Dirofilaria antigen tests were detected in dogs with heart disease or heart failure. Serum NT-proBNP concentrations of dogs with heart failure (2,977 +/- 184 pmol/l) were significantly higher than dogs with heart disease (611 +/- 46 pmol/l), respiratory disease (583 +/- 52 pmol/l) or physically healthy (426 +/- 32 pmol/l). In dogs with heart failure, the serum NT-proBNP concentrations from the female dogs (3,291 +/- 266 pmol/l) were slightly higher than the male dogs (2,770 +/- 247 pmol/l), but did not reach the statistical significant. Dirofilaria infections were also found in dogs with heart disease (n=9) and dogs with heart failure (n=7). Interestingly, NT-proBNP concentration from Dirofilaria infected dogs with heart disease (533 +/- 53 pmol/l) was significantly lower than Dirofilaria infected dogs with heart failure (2,576 +/- 504 pmol/l). Different cut-off values (at 300, 600 and 900 pmol/l) were used to discriminate the dogs with heart failure from other groups, high cut off values slightly reduced percent sensitivity (98.3%, 93.1% and 93.1%, respectively) while significantly improved percent specificity (7.7%, 59.0% and 92.3%, respectively). In conclusion, the serum NT-proBNP levels were comparable in dogs with and without heart diseases except including the heart failure dogs. Furthermore, gender and Dirofilaria infection did not influence in the serum NT-proBNP concentration. The use of higher cut-off values for serum NT-proBNP significantly improves specificity of the test for the diagnosis of congestive heart failure in dogs with respiratory distress.