Usefulness of High Sensitivity Troponin T Assay in Detecting Acute Allograft Rejection After Heart Transplantation

Abstract

Introduction and objectives Detection of acute allograft rejection in heart transplant recipients by noninvasive methods is a challenge in the management of these patients. In this study, the usefulness of a new highly sensitive method for the measurement of troponin T is evaluated. Methods We designed a case-crossover study, in which each patient served as his or her own control, by selecting samples from treated acute rejection episodes (29 cases) and samples obtained immediately before and/or after rejection (38 controls). The highly sensitive troponin T was measured by a new pre-commercial test (Elecsys Troponin T HS). Results In all samples, highly sensitive troponin was detectable, with a median of 0.068 ng/mL (IQR, 0.030-0.300 ng/mL). The levels correlated with right atrial pressure (r = 0.37; P = .002), N-terminal pro-brain natriuretic peptide concentration (r = 0.67; P < .001), and time since transplantation (r = –0.81; P < .001). The highly sensitive troponin concentrations were higher in patients with rejection (0.155 ng/mL vs 0.047 ng/mL; P = .006). In the receiver operating characteristic analysis, the area under the curve was 0.67 (95% confidence interval, 0.53-0.77) and the best cutoff was 0.035 ng/mL, which was associated with rejection (odds ratio = 3.7; 95% confidence interval, 1.2-11.9; P = .02). By restricting the analysis to the first 2 months, the area under the curve increased to 0.86 (95% confidence interval 0.66-0.97), with an optimal cutoff of 1.10 ng/mL (S = 58% [28%-85%]; E = 100% [74%-100%]). Conclusions Troponin T was detectable in all samples when a new highly sensitive assay was used, and at higher concentrations in the presence of acute rejection; however, the usefulness of this test in patient management is limited to support for clinical or histological suspicion of rejection, especially in the early post-transplant period.