In congestive heart failure (CHF), increased activity of the adrenergic system, overexpression of atrial and brain natriuretic peptides (ANP and BNP), activation of the renin-angiotensin-aldosterone system, and increased synthesis and release of endothelin (ET) have been observed. In humans, plasma concentrations of ANP and BNP and their N-terminal propeptides have been shown to have prognostic value. Most commercial kits used for veterinary patients are designed for human use, but there is reason to believe some crossreactivity exists among mammalian species. In this study, 8 immunoassays for cardiac biomarkers were assessed for accuracy and reproducibility in dogs. Plasma samples from 27 healthy dogs and 3 dogs with CHF were used, and assay validation was performed in a 2-step process. Preliminary validation included determination of intraassay variability and dilutional parallelism. Kits showing good results in the preliminary validation were further validated by determining precision, linearity, and accuracy. Performance was found to differ considerably among the assays. Based on study results, 4 of the 8 assays (proANP, BNPPhoe, ET-1IBL, and Big-ETIBL) were found to be precise, reproducible, linear, and accurate and could thus be recommended for use in dogs.

COMMENTARY: The use of biomarkers to diagnose cardiac disease in veterinary medicine has garnered tremendous interest over the past 5 to 10 years. Some of these markers have promise to help differentiate dyspnea caused by CHF from noncardiac causes in dogs. However, while they provide supportive evidence of CHF, the definitive diagnosis cannot be made based on the results of these biomarkers alone. The use of BNP in cats may be more reliable in this manner. This article does not try to answer the clinical question of how reliable these assays are in diagnosing CHF. Instead, it focuses on whether these markers are accurately measured by some commercially available assays. Based on the results, most assays evaluated performed fairly well under what would be considered normal clinical conditions.

Analytical validation of commercial immunoassays for the measurement of cardiovascular peptides in the dog. Schellenberg S, Grenacher B, Kaufmann K, et al. VET J; Aug 2007.