Validation of an immunoassay for measurement of canine cardiac troponin-I

Cardiac troponin-I (cTnI) is a sensitive and specific circulating marker of cardiac injury. The amind acid sequence of canine troponin-I suggests that immunoassays designed for humans may be able to quantify canine cTnI. We sought to validate the AccuTnI™ system for use in the canine species. Samples of purified canine free cTnI, cardiac troponin I-C (cTnI-C), and cardiac troponin I-T-C (cTnI-T-C) were used to assess the performance characteristics of the assay. Intra-assay precision was 4.2 ± 3.0% and inter-assay precision was 4.5 ± 2.7%. The assay demonstrated linearity of serial dilutions from 0.015 to 30 ng/ml for all forms of cTnI (R, 0.998 to 0.999). Mean recovery of cTnI was 92.5 ± 10.5%, of cTnI-C was 147.2 ± 19.8%, and of cTnI-T-C was 97.3 ± 23.5%. Specificity of the assay for the cardiac form of troponin-I was confirmed using samples spiked with canine skeletal muscle troponin-I. The AccuTnI™ assay was evaluated in 27 canine patients. Dogs with heart disease (cardiomyopathy or severe mitral valve disease, n = 13) had a higher mean cTnI concentration than controls (disease cTnI = 0.68 ng/ml, range 0.03-5.47 ng/ml vs. control cTnI = 0.03 ng/ml, range 0.01-0.08 ng/ml; P = 0.0003). The AccuTnI™ assay possesses sufficient test performance for use with canine plasma and can distinguish a cohort of dogs with heart disease from a cohort of healthy controls. The results of this study suggest that further investigations into the clinical use of the AccuTnI™ assay for the diagnosis of canine heart disease are warranted.