Validation of the ADVIA Centaur® Immunoassay for the Measurement of Bovine Cardiac Troponin I
The use of cardiac troponin I (cTnI) as a sensitive and specific biomarker of myocardial injury has been well established in people, small animals, and horses. Prospective studies on the use of cTnI in cattle are lacking. The objective of this study was to validate the ADVIA Centaur®CP Immunoassay System (Bayer Healthcare Diagnostics, Newbury, UK) for the detection of serum bovine cTnI concentrations and to establish a reference range for healthy dairy cows.
Different concentrations of purified bovine cTnI (BiosPacific, Emeryville, CA) were diluted into cTnI-free bovine serum and used to assess sensitivity, precision, linearity, and recovery of the ADVIA Centaur® assay. Intra and inter-assay precision (reported as the mean coefficient of variation (CV)) were measured at serum concentrations of 0.2, 1.0, 10 and 30 ng/ml of cTnI. Intra-assay precision was < 5% and inter-assay precision was < 12%. The assay demonstrated linearity of serial dilutions from 0.05 to 30 ng/ml cTnI. Test recovery ranged from 70 % up to 110 % depending on the cTnI concentration in serum. No cross reactivity of the assay with homogenized skeletal muscle was observed. Stability of bovine cTnI was determined by analysis of different cTnI concentrations stored at room temperature for 2 days and at 4°C and -80°C for 2, 7, and 14 days. A relevant decrease of cTnI concentrations over time was observed when samples were stored at room temperature and at 4°C. Storage at -80° C as well as repeated freeze-thaw cycles did not affect cTnI concentrations.
In healthy dairy cows (n=20) serum cTnI concentrations were below the lower limit of detection (0.01 ng/ml) of the assay in 5 and between 0.01 and 0.03 ng/ml in the other 15 cows.
Our preliminary results indicate the ADVIA Centaur® immunoassay developed for use in people may have adequate test performance for the detection of circulating bovine cTnI. This assay may be useful in the early identification of myocardial injury secondary to infectious, toxic, and inflammatory insults in cattle. Studies in dairy cows with myocardial disease are needed to clinically validate our findings.