Correlation between troponin I serum level and acute cardiac allograft rejection: a preliminary report

Elevated Cardiac Troponin to Detect Acute Cellular Rejection After Cardiac Transplantation: A Systematic Review and Meta-Analysis

Cardiac troponin is well known as a highly specific marker of cardiomyocyte damage, and has significant diagnostic accuracy in many cardiac conditions. However, the value of elevated recipient troponin in diagnosing adverse outcomes in heart transplant recipients is uncertain. We searched MEDLINE (Ovid), Embase (Ovid), and the Cochrane Library from inception until December 2020. We generated summary sensitivity, specificity, and Bayesian areas under the curve (BAUC) using bivariate Bayesian modelling, and standardised mean differences (SMDs) to quantify the diagnostic relationship of recipient troponin and adverse outcomes following cardiac transplant. We included 27 studies with 1,684 cardiac transplant recipients. Patients with acute rejection had a statistically significant late elevation in standardised troponin measurements taken at least 1 month postoperatively (SMD 0.98, 95% CI 0.33–1.64). However, pooled diagnostic accuracy was poor (sensitivity 0.414, 95% CrI 0.174–0.696; specificity 0.785, 95% CrI 0.567–0.912; BAUC 0.607, 95% CrI 0.469–0.723). In summary, late troponin elevation in heart transplant recipients is associated with acute cellular rejection in adults, but its stand-alone diagnostic accuracy is poor. Further research is needed to assess its performance in predictive modelling of adverse outcomes following cardiac transplant.

Systematic Review Registration: identifier CRD42021227861

Utility of troponin assays for exclusion of acute cellular rejection after heart transplantation: A systematic review

BACKGROUND

Acute cellular rejection (ACR) is a common complication in the first year after heart transplantation (HT). Routine surveillance for ACR is undertaken by endomyocardial biopsy (EMB). Measurement of cardiac troponins (cTn) in serum is an established diagnostic test of cardiac myocyte injury. This systematic review aimed to determine whether cTn measurement could be used to diagnose or exclude ACR.

METHODS

PubMed, Google Scholar and the JHLT archive were searched for studies reporting the result of a cTn assay and a paired surveillance EMB. Significant ACR was defined as International Society for Heart and Lung Transplantataion (ISHLT) Grade ≥3a/≥2R. Considerable heterogeneity between studies precluded quantitative meta-analysis. Individual study sensitivity and specificity data were examined and used to construct a pooled hierarchical summary receiver-operator characteristic (ROC) curve.

RESULTS

Twelve studies including 993 patients and 3,803 EMBs, of which 3,729 were paired with cTn levels, had adequate data available for inclusion. The overall rate of significant ACR was 12%. There was wide variation in diagnostic performance. cTn assays demonstrated sensitivity of 8% to 100% and specificity of 13% to 88% for detection of ACR. The positive predictive value (PPV) was low but the negative predictive value (NPV) was relatively high (79% to 100%). High-sensitivity cTn assays had greater sensitivity and NPV than conventional cTn assays for detection of ACR (sensitivity: 82% to 100% vs 8% to 77%; NPV: 97% to 100% vs 81% to 95%, respectively).

CONCLUSIONS

cTn assays do not have sufficient specificity to diagnose ACR in place of EMB. However, hs-cTn assays may have sufficient sensitivity and negative predictive value to exclude ACR and limit the need for surveillance EMB. Further research is required to assess this strategy.

Advances in diagnostics for transplant rejection

INTRODUCTION

Identification of allograft injury, including acute clinical and subclinical injury, is vital in increasing the longevity of the transplanted organ. Acute rejection, which occurs as a result of a variety of immune and non-immune factors including the infiltration of immune cells and antibodies to the donor specific epitopes, poses a significant risk to the organ. Recent years have marked an increase in the discovery of new genomic, transcriptomic, and proteomic biomarkers in molecular diagnostics, which offer better potential for personalized management of the transplanted organ by providing earlier detection of rejection episodes. Areas covered: This review was compiled from key word searches of full-text publications relevant to the field. Expert commentary: Many of the recent advancements in the molecular diagnostics of allograft injury show much promise, but before they can be fully realized further validation in larger sample sets must be conducted. Additionally, for better informed therapeutic decisions, more work must be completed to differentiate between different causes of injury. Moreover, the diagnostics field is looking at methodologies that allow for multiplexing, the ability to identify multiple targets simultaneously, in order to provide more robust biomarkers and better understanding.

Usefulness of high-sensitivity troponin I for the monitoring of subclinical acute cellular rejection after cardiac transplantation

BACKGROUND

There are conflicting data about the role of cardiac troponin I (cTnI) as determined by means of conventional methods for the prediction of acute rejection after heart transplantation (HT). The purpose of this study was to evaluate whether cTnI as measured by means of the early prototype high-sensitivity assay (hs-cTnI) can predict acute rejection episode after HT compared with grade of rejection in endomyocardial biopsy (EMB).

METHODS

This was a single-center cross-sectional study evaluating cTnI levels with the use of both hs-cTnI and current less sensitive conventional cTnI (conv-cTnI) assays measured at the time of EMB after HT. We calculated an index ratio of observed cTnI to expected mean cTnI for each individual patient defined as the mean cTnI measurements at EMB 60 days after HT.

RESULTS

A total of 252 biopsies from 47 patients were included in this study. In the multivariable mixed model analysis in relation to the presence of acute rejection 60 days after HT, hs-cTnI level was significantly related to the presence of rejection (P = .010). The hs-cTnI ratio index was significantly higher at the time of rejection (median, 1.37; interquartile range [IQR], 1.23-2.88) compared with those without rejection (median, 0.90; IQR, 0.51-1.16; P < .001). In receiver operating characteristic curve analysis, an hs-cTnI ratio index of ≥1.17 could predict the acute rejection with a sensitivity of 82.4% and a specificity of 77.1%.

CONCLUSIONS

An increased hs-cTnI ratio index was significantly related to rejection episodes. Serial monitoring of hs-cTnI and comparing it with the values without rejection might be useful for the detection of acute rejection after HT.

High-sensitivity cardiac troponin I assay to screen for acute rejection in patients with heart transplant

BACKGROUND

A noninvasive biomarker that could accurately diagnose acute rejection (AR) in heart transplant recipients could obviate the need for surveillance endomyocardial biopsies. We assessed the performance metrics of a novel high-sensitivity cardiac troponin I (cTnI) assay for this purpose.

METHODS AND RESULTS

Stored serum samples were retrospectively matched to endomyocardial biopsies in 98 cardiac transplant recipients, who survived ≥3 months after transplant. AR was defined as International Society for Heart and Lung Transplantation grade 2R or higher cellular rejection, acellular rejection, or allograft dysfunction of uncertain pathogenesis, leading to treatment for presumed rejection. cTnI was measured with a high-sensitivity assay (Abbott Diagnostics, Abbott Park, IL). Cross-sectional analyses determined the association of cTnI concentrations with rejection and International Society for Heart and Lung Transplantation grade and the performance metrics of cTnI for the detection of AR. Among 98 subjects, 37% had ≥1 rejection episode. cTnI was measured in 418 serum samples, including 35 paired to a rejection episode. cTnI concentrations were significantly higher in rejection versus nonrejection samples (median, 57.1 versus 10.2 ng/L; P<0.0001) and increased in a graded manner with higher biopsy scores (P(trend)<0.0001). The c-statistic to discriminate AR was 0.82 (95% confidence interval, 0.76-0.88). Using a cut point of 15 ng/L, sensitivity was 94%, specificity 60%, positive predictive value 18%, and negative predictive value 99%.

CONCLUSIONS

A high-sensitivity cTnI assay seems useful to rule out AR in cardiac transplant recipients. If validated in prospective studies, a strategy of serial monitoring with a high-sensitivity cTnI assay may offer a low-cost noninvasive strategy for rejection surveillance.

Cardiac troponin I: a marker of acute heart rejection in infant and child heart recipients?

Acute rejection of the donor heart is a major cause of mortality in infant heart transplant recipients. The early diagnosis of acute cardiac rejection (ACR) is crucial. Non-invasive methods have shown poor sensitivity in detecting rejection when compared to endomyocardial biopsies (EMB). We assessed troponin I as a new marker to diagnose cardiac rejection. Serum cardiac troponin I (cTNI) levels were retrospectively analysed in 25 heart transplant patients (ages, 2 wk to 13 yr; mean age, 3 months) presenting 36 acute rejections. In early post-operative rejection and initially elevated cTNI levels, rejection was associated with a second increase of serum cTNI concentrations in 21% of the patients (p = 0.15). If cTNI levels were in normal range before ACR an elevation was monitored in 59% of the rejection periods (p < 0.05). In 25% of the cases (n = 9) cTNI levels remained in normal range during the rejection episode (<0.6 ng/mL), in 22% (n = 8) cTNI levels did not exceed pathological values from 0.6 to 1.5 ng/mL and in 53% (n = 19) the measured levels went beyond 1.5 ng/mL. Maximum concentrations of cTNI were measured mostly 12 d from the moment rejection was suspected (day 1) in patients (median day 3). However, cTNI levels were elevated for 2-43 d after ACR was diagnosed (median 10 d). Twenty per cent of the patients with grade 3 rejection (ISHLT) and 75% of the patients with grade 4 rejection had a corresponding elevated cTNI level (p = 0.013). No false-positive elevations of cTNI were documented. The present data demonstrate that cTNI is a not a sensitive but a specific marker of ACR in children.