Analytical validation of a high-sensitivity cardiac troponin T assay in horses

Although cardiac troponin T (cTnT) assays have been used to detect myocardial damage in horses, a cTnT assay has not been analytically validated, to our knowledge. The aims of this study were to estimate the precision of a high-sensitivity cTnT assay in horses and determine the effect of hemolysis on the measured cTnT concentration. Serum samples from horses were mixed in 3 different pools. Pool 1 consisted of samples from 3 healthy horses, pool 2 from 6 horses with heart failure or atypical myopathy, and pool 3 from 10 horses with atypical myopathy. The within- and between-run coefficients of variation were determined for each pool. Pools 2 and 3 were diluted to estimate linearity. To study the influence of sample hemolysis, serum was collected from 4 horses with a high cTnT concentration, in which hemolysis was mechanically induced. In addition, ethylenediamine tetra-acetic acid blood tubes were collected from 3 other horses, from which hemolysate was prepared and added to plasma at different concentrations. The within- and between-run coefficients of variation of all pools were <10%, and a good linearity was found. Three out of 4 hemolyzed serum samples had a decreased serum cTnT concentration. Plasma samples with a high hemolysis index showed a negative interference, resulting in a lower cTnT concentration. Results of the high-sensitivity cTnT assay were highly reproducible. Because samples from horses with musculoskeletal damage were included, further studies should test the possible cross-reactivity between troponin T of musculoskeletal and cardiac origin before the assay can be used in equine clinical practice.