Cardiac Troponin I in Racing Standardbreds

Abstract

Background Upper reference limits for cTnI have not been established for healthy Standardbred racehorses. Objectives To establish cTnI upper reference limits for Standardbred racehorses and determine if increases in plasma cTnI concentration can be detected in 1–2 hours after a race. Animals Samples were obtained from 586 apparently healthy Standardbreds aged 2–14 years before racing and from the winners of 144 races 1–2 hours after the end of the race. Methods Prospective, observational study; convenience sampling; assay validation; and reference limits determinations were performed according to ASCVP guidelines. Plasma cardiac troponin I concentrations before racing were determined, potential outliers identified, and the 95th and 99th percentile upper reference limits calculated using nonparametric methods. The correlation between cTnI concentration and age, differences in median cTnI concentrations by subgroups and differences between cTnI concentrations before and after racing in winning horses were determined. Results The 95th and 99th percentile upper reference limits for all horses excluding outliers were < 0.04ng/mL and 0.06 ng/mL. There were no significant differences in cTnI concentrations based on age (P = .06), sex (P = .35), gait (P = .55), or race classification (P = .65) and a weak correlation of cTnI with age (ρ = 0.09, P = .03). There were no significant differences between cTnI concentrations before and after racing in winning horses (P = .70). Conclusions and Clinical Importance Because of lack of standardization across cTnI assays, the reference limits apply only to the Stratus CS immunoassay. Future studies looking at the effects of high intensity, short duration exercise on cTnI should consider sampling more than 2 hours after racing or using an ultrasensitive assay.

24‐Hour Kinetics of Cardiac Troponin‐T Using a “High‐Sensitivity” Assay in Thoroughbred Chuckwagon Racing Geldings after Race and Associated Clinical Sampling Guidelines

“…Seven research studies in horses have evaluated cTn concentrations in normal horses after nonendurance exercise. None of these studies identified significant increases in cTn concentrations partly as a consequence of the study population sizes (15, 28, 6, 24, 26, and 15 horses, respectively) but also as a result of the use of older generation, conventional sensitivity assays that have a higher LoD . We identified significant increases in cTn, using the hscTnT assay, in horses after high‐intensity, short‐duration racing exercise.…”

“…application of established reference population, URL). In horses, a weak positive age, but not sex, correlation has been corroborated in 1 study of 586 Standardbreds at rest . Age correlations also have been explored in subjects undergoing exercise challenges, and in a recent cTnT postexercise study of humans using a high‐sensitivity assay, no age correlation was found between age and peak postexercise cTn concentrations.…”

“…This observation illustrates 1 of the benefits of using a high‐sensitivity cTn assay that is >10‐fold more sensitive as compared to conventional cTn assays, and confirms conforming to the CLSI criteria that high‐sensitivity assays must measure cTn concentrations in at least 50% of the population at rest. The ability of the present hscTnT assay to function reliably at these low concentrations (LoQ) is unique when compared to the only cTnI assay similarly validated appropriately by ASVCP and CLSI standards for use in horses . Because all assays for cTnT are marketed by 1 manufacturer,b and instruments are calibrated to the same reference material, analysis, and standardization are beneficially more straightforward than for cTnI.…”

“…The effects of age on baseline and postexercise troponin concentrations have been evaluated in humans . Another report in horses examined the effects of age on baseline and postexercise troponin‐I concentrations . In horses, no such correlations among age, baseline cTnT concentrations, and cTnT release after exercise have been explored.…”

Overview of Clinical Pathology and the Horse

“…51 Troponin levels and their behavior in association with anesthesia, racing, training, and endurance exercise has also been studied. [52][53][54][55][56] Increased CTNI levels in horses with colic support a less favorable prognosis and are associated with increased ventricular arrhythmias postoperatively. In one study, the combination of high CTNI levels postoperatively and high lactate levels preoperatively were significantly associated with nonsurvival.…”