Accuracy of four quick tests for canine distemper antibodies in dogs

Abstract

Pre-vaccination antibody testing to determine dogs' immunity against canine distemper virus (CDV) is increasingly used. Four point-of-care tests (POC A-D) are available in Europe, but their diagnostic accuracy has not been compared. The study evaluated the diagnostic accuracy and usability of these tests. Sera of client-owned dogs (n = 198; healthy n = 22; unhealthy dogs n = 176) and specific pathogen-free (SPF) dogs (n = 40) were included. Virus neutralisation (VN) was performed as the reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy (OA) were determined. McNemar's test was used to determine significant differences between specificity and sensitivity of the tests and Cohen's kappa was used to assess agreement. The prevalence of anti-CDV antibodies by VN was 80% in client-owned dogs overall, with 100% prevalence in healthy dogs, and 0% in SPF dogs. POC-C and POC-D were considered easiest to perform. Specificity of all tests was high using sera from SPF dogs (88-100%). In healthy dogs, sensitivity was variable (45-98%). Specificity was low in all four POC tests when using sera from acutely ill dogs (6-53%) and clinically healthy dogs with chronic disease (5-77%). In client-owned dogs, including healthy and unhealthy dogs, agreement was poor between tests. All POC tests had a low specificity when investigating sera from ill client-owned dogs and usefullness of these tests especially in dogs that are acutely ill or have chronic disease is not supported by this study.