Assessment of the diagnostic accuracy of circulating natriuretic peptide concentrations to distinguish between cats with cardiac and non-cardiac causes of respiratory distress David J. Connolly, BSc, BVetMed, PhD a, *, Ricardo J. Soares Magalhaes, DVM, MSc b , Virginia Luis Fuentes, MA, VetMB, PhD a , Adrian Boswood, MA, VetMB a , Georgina Cole, BvetMed a , Alisdair Boag, BVetMed a , Harriet M. Syme, BSc, BVetMed, PhD a a Department of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA, UK b School of Population Health, University of Queensland, Herston Road, Herston, QLD 4105, Australia KEYWORDS Cardiac biomarkers; Respiratory distress; Sensitivity; Specificity Abstract Objectives: To determine if serum natriuretic peptide (NP) concentra- tions could distinguish cardiac from non-cardiac causes of respiratory distress (RD) in cats. Animals: Seventy-four cats from 1 university hospital were used. Methods: Serum NP concentrations were measured in 41 cats with non-cardiac respiratory distress (RD-NC) and compared to 33 cats with RD due to congestive heart failure (RD þ CHF) using sandwich enzyme immunoassays (ELISA). Results: RD-NC cats had lower (P ¼ 0.0001) median NT-proANP and NT-proBNP concentrations (614 and 45 fmol/mL, respectively) than RD þ CHF cats (1690 and 523 fmol/mL, respectively). The area under the curve was 0.88 and 0.96 for the receiver operating curve analysis of the diagnostic accuracy of NT-proANP and NT-proBNP concentrations to discriminate RD þ CHF from RD-NC cats (P ¼ 0.036). An optimum cut-off concentration of 986 fmol/mL for NT-proANP and 220 fmol/ mL for NT-proBNP accurately discriminated RD-NC from RC þ CHF cats with a sensi- tivity of 93.8% and 93.9% and a specificity of 80.3% and 87.8%, respectively. * Corresponding author. E-mail address: dconnolly@rvc.ac.uk (D.J. Connolly). 1760-2734/$ - see front matter ª 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jvc.2009.03.001 Journal of Veterinary Cardiology (2009) 11, S41eS50 www.elsevier.com/locate/jvc