Detection by ELISA of C-terminal proBNP in plasma from cats with cardiomyopathy

•We describe a laboratory validated sandwich ELISA for feline C-terminal B-type natriuretic peptide prohormone (proBNP).•C-terminal proBNP circulates in the plasma of cats with cardiomyopathy.•proBNP concentrations are similar to those found in human heart failure patients.•Most proBNP immunoreactivity in feline plasma is biologically inactive. The B-type natriuretic peptide prohormone (proBNP) is enzymatically cleaved into an inactive N-terminal peptide and a biologically active C-terminal peptide with many beneficial cardiorenal effects. The purpose of this study was to develop and test in cats with cardiomyopathy an immunoassay to quantify the concentrations of C-terminal proBNP in feline plasma. An anti-canine proBNP monoclonal antibody (UI-1021) was shown to have adequate binding affinity to proBNP 80–106 for use in a solid-phase immunoassay, and by epitope mapping to bind within positions 84–87 of feline proBNP. UI-1021 was paired with an affinity-purified rabbit polyclonal detection antibody to feline proBNP 100–106, in a sandwich ELISA with feline proBNP 80–106 standard. The linearity and analytical range and sensitivity of the assay were confirmed from 1.4 to 85 pmol/L. Spike recovery averaged 106.5% (95% confidence interval 78–135%). Within run and intra-assay coefficients of variation were