Utility of measuring plasma N-terminal pro-brain natriuretic peptide in detecting hypertrophic cardiomyopathy and differentiating grades of severity in cats

Background: Cats with hypertrophic cardiomyopathy (HCM) often have no clinical signs or subtle signs. Measurement of N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) has been demonstrated in people to be highly specific for heart disease and also correlates with severity of HCM. NT‐proBNP may also be valuable in detecting and grading HCM in cats, but results to date have been equivocal. Objectives: The aims of this study were to evaluate NT‐proBNP as a screening test for diagnosis of HCM in cats and determine an appropriate cut‐off value and to determine if NT‐proBNP concentrations correlated with severity of HCM in cats. Methods: Plasma NT‐proBNP concentrations were measured in 201 cats using an ELISA designed for use in cats. Cats were classified using echocardiography as clinically healthy controls (n=99) or cats with equivocal (n=9), mild (n=15), moderate (n=17), or severe (n=61) HCM. Results: NT‐proBNP concentrations (median; 25th–75th interquartile percentiles) in mildly (216.1; 87.6–392.5 pmol/L), moderately (282.7; 131.9–466.6 pmol/L), and severely (839.5; 655.3–1046.4 pmol/L) affected cats were significantly higher than those in healthy controls (18.9; 3.4–62.4 pmol/L). Concentrations in severely affected cats were significantly higher than in cats from other HCM groups. There was no significant difference between mild and moderate HCM. Cut‐off values >49 pmol/L had a sensitivity of 97.8% and specificity of 66.7%; >100 pmol/L had a sensitivity of 92.4% and specificity of 93.9%; and >150 pmol/L had a sensitivity of 88% and a specificity of 100%. Conclusions: NT‐proBNP with a cut‐off value of >100 pmol/L was useful in detecting even mild HCM. Cats with increased NT‐proBNP concentrations should be examined by echocardiography.