Cardiac biomarkers are commonly used to screen for heart disease. In particular, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) has proven valuable in detecting both clinical and preclinical cardiomyopathies in cats. However, NT-proBNP levels can also rise due to other conditions, such as chronic kidney disease (CKD), systemic hypertension, and hyperthyroidism, potentially complicating the interpretation of results in patients with multiple health issues.

The primary aim of this study is to characterize serum NT-proBNP concentrations in cats with varying severities of CKD, as classified by the International Renal Interest Society (IRIS) staging. Additionally, the study will compare NT-proBNP serum concentrations in cats with CKD to cats with preclinical hypertrophic cardiomyopathy (HCM

Cats with CKD will be prospectively assigned to one of four groups based on IRIS staging of CKD, with healthy cats without CKD serving as controls. Cats with uncontrolled hyperthyroidism, systemic hypertension, significant arrhythmias, or structural/functional cardiac abnormalities outside reference ranges will be excluded. After enrollment, NT-proBNP serum concentrations will be measured. These concentrations will be compared across the five groups using analysis of variance (or Kruskal-Wallis test for nonparametric data) with post-hoc pairwise comparisons. Correlations between NT-proBNP levels and renal function markers (blood urea nitrogen, creatinine, and symmetric dimethylarginine) will be evaluated using Pearson’s or Spearman’s rank correlation. Additionally, NT-proBNP levels will be measured in a cohort of cats with preclinical HCM without CKD. NT-proBNP will be compared between the CKD group and the HCM group using a 2-sample t-test (or Mann-Whitney test for nonparametric data).

Enhancing the characterization of NT-proBNP in cats with CKD and comparing these established values with measured NT-proBNP levels in cats with preclinical HCM will increase its clinical usefulness in distinguishing NT-proBNP elevations caused by CKD from those linked to cardiac disease in cats.