Analytical validation and clinical evaluation of a high-sensitivity cardiac troponin I immunoassay for use in cats

Cardiac troponin I (cTnI) is a cardiac specific biomarker of myocardial damage in humans, dogs, and cats. The ADVIA Centaur XP High-Sensitivity Troponin I assay (AC-cTnI-HS) has been validated for use in humans and dogs, but not for use in cats. The study objective was to analytically validate the AC-cTnI-HS assay for use in cats and to evaluate cTnI measurements in healthy cats compared to those with cardiac disease to assess the clinical utility of this assay. Surplus serum samples from cats were used for analytical validation. Intra- and inter-assay variability, dilutional parallelism, and spiking recovery were assessed. Serum samples from 106 client-owned cats were evaluated. This group was comprised of 51 clinically healthy cats (structurally normal echocardiogram, normal systemic blood pressure, and unremarkable complete blood count and biochemistry profile), 25 cats with stage B1 hypertrophic cardiomyopathy, 7 with stage B2 hypertrophic cardiomyopathy, 7 with stage C cardiomyopathy of any type, 8 with congenital heart disease, and 8 cats with transient myocardial thickening and/or suspected to have myocarditis. Inter-assay and intra-assay coefficients of variation were between 2.7-8.3% and 1.5-4.0%, respectively. The mean ± standard deviation observed to expected ratios for dilutional parallelism and spiking recovery were 124.3 ± 42.8% and 92.9 ± 6.2%, respectively. Healthy cats had significantly lower cTnI concentrations than cats with hypertrophic cardiomyopathy stage B1 (P = 0.012), stage B2 (P = 0.004), or any cardiomyopathy ACVIM stage C (P = 0.002). The AC-cTnI-HS assay is precise, reproducible, linear, and accurate for measurement of cTnI concentrations in serum from cats. This study confirms that measurement of serum cTnI holds promise to have clinical utility as it was able to detect differences in serum cTnI concentrations between healthy cats and those with cardiac disease.