# The role of high-sensitivity troponin in identifying patients with cardiac allograft rejection

## TL;DR

This study shows that high-sensitivity troponin I can help identify heart transplant patients with acute rejection, especially in a Latin American population with diverse causes like Chagas disease.

## Contribution

The study is the largest Latin American cohort to assess hs-TnI after heart transplant and the first to explore its performance in specific etiologies including Chagas disease.

## Key findings

- Higher hs-TnI levels were significantly associated with acute cellular rejection (ACR >2R) compared to lower grades.
- A cutoff of 19 ng/L for hs-TnI showed 88% sensitivity and 92% negative predictive value for ACR >2R.
- hs-TnI demonstrated significant discriminatory power for ACR >2R in patients with Chagas disease.

## Abstract

Biomarkers for acute rejection diagnosis are frequently searched, and data from medical literature are conflicting. The role of high-sensitivity troponin I in the diagnosis of acute cellular rejection (ACR) after heart transplant (HT) is uncertain. However, it is a widely used and accessible tool in developing countries.

This study aims to determine whether hs-TnI can serve as a reliable and accessible tool to identify patients with clinically significant rejection (ACR >2R) in a real-world Latin American cohort that has different etiologies than the epidemiology of the main trials.

In this retrospective cohort, we evaluated data from electronic records of HT recipients submitted to HT from March, 2020 to September, 2022 using REdCAp database. All patients who underwent endomyocardial biopsies (EMB) between 3 months and 2 years of HT and had samples of HS-troponin I previously measured were included in this study. The HS-troponin levels were compared between patients with ACR higher or lower than 2R.

In this analysis, we included data from 187 biopsies performed at least 3 months after HT in 94 recipients who had paired Hs-troponin I samples collected. Fifty-four (57%) were men, and their median age at heart transplant was 48 ±11 years. The median hs-TnI levels were 29 (11-118) ng/L. ACR > 2R was observed in 48 EMB and the median hs-TnI levels were 69 (26-224) ng/L, which was significantly higher than levels observed in patients with grade 0R/1R [21 (9-64) ng/L, p<0.001]. The ROC curve of hs-TnI shows an AUC of 0.705; p<0.001 for the diagnosis of ACR > 2R. A cutoff of 19 ng/L showed a sensitivity of 88% and specificity of 49%, with a negative predictive value of 92%. Among biopsies from patients with Chagas disease (36.9% of the sample), hs-TnI also showed significant discriminatory power for ACR >2R (p = 0.037).

In this cohort, HS-troponin I was able to identify patients with acute cellular rejection. This is the largest Latin American cohort assessing hs-TnI after HT, and the first to explore its performance across specific etiologies, including Chagas disease. Prospective studies may confirm the role of HS-troponin I as a biomarker of acute rejection.