Copeptin Hormone Concentrations in Dogs with Heart Disease and Relationship with Antidiuretic Hormone

Antidiuretic hormone (ADH) is upregulated in dogs with cardiac disease. However, measurement of ADH is impractical in a clinical setting. Copeptin is co-secreted with ADH, making it a potential biomarker of ADH secretion. We hypothesized that dogs with cardiac disease would upregulate copeptin concentrations and that copeptin would positively correlate with ADH, serum chloride ([Cl^-]), and degree of mathematical [Cl^-] correction. The study population comprised 19 healthy, 20 preclinical (Stage B), and 20 congestive heart failure (CHF, Stage C or D) dogs. Groups were compared with Kruskal-Wallis tests. The agreement between ADH and copeptin was assessed with Bland-Altman analysis. Relationships between copeptin and clinical variables were explored using multivariable linear regression. There were no significant differences in copeptin concentrations among healthy (median 54.9 pg/mL; range 0.5-196.1), preclinical (median 43.6 pg/mL; range 0.5-131.4), and CHF (median 60.5 pg/mL; range 0.5-997.8) dogs (p = 0.76). Relative to ADH, copeptin showed a negative proportional bias of -87.8 pg/mL with wide limits of agreement (-421.8 to 246.2). Linear regression showed a significant influence of age on copeptin concentration. Copeptin measured by ELISA does not reflect the ADH concentration in healthy dogs or in dogs with cardiac disease. Copeptin concentrations are, however, inversely associated with age.