Analytical validation and clinical evaluation of a commercially available high-sensitivity immunoassay for the measurement of troponin I in humans for use in dogs.
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OBJECTIVE: To analytically validate a commercially available high-sensitivity immunoassay for measurement of cardiac troponin I (cTnI) in humans for use in dogs and to evaluate serum cTnI concentrations in healthy dogs and 3 well-defined groups of dogs with common cardiac diseases. ANIMALS: Canine serum samples were used for validation. 85 client-owned dogs including 24 healthy controls, 20 with myxomatous mitral valve disease, 19 with congenital heart disease, and 22 with arrhythmias. METHODS: Four serum samples were used to analytically validate the ADVIA Centaur TnI-Ultra assay by assessing intra-assay variability, inter-assay variability, spiking recovery, and dilutional parallelism. Dogs were grouped based on examination, echocardiography, and additional testing as clinically indicated, and serum cTnI concentrations were compared. RESULTS: Analysis of the serum samples used for validation revealed an intra-assay coefficient of variation between 3.6% and 5.7%, and an inter-assay coefficient of variation between 2.4% and 5.9%. Observed to expected ratios for spiking recovery were 97.98.6% (mean, SD). Observed to expected ratios for dilutional parallelism were 73.011.5% (mean, SD). Dogs with cardiac disease had significantly higher serum cTnI concentrations (P<0.005) than healthy dogs. CONCLUSIONS: The ADVIA Centaur TnI-Ultra's low limit of detection allows measurement of serum cTnI in the majority of dogs even with no or mild cardiac disease. Dilution of samples for measurement of values above the upper limit of detection is not reliable and therefore not recommended. Serum cTnI concentrations are significantly higher in dogs with cardiac disease compared to healthy dogs.