Use of a highly sensitive assay for cardiac troponin T and N-terminal pro-brain natriuretic peptide to diagnose acute rejection in pediatric cardiac transplant recipients.

Background: Biomarkers have been proposed to augment or replace endomyocardial biopsy (EMB) to diagnose acute transplant rejection (AR). A new, highly sensitive assay for troponin T detects levels of cardiac troponin T (cTnT) 10- to 100-fold lower than standard assays but has not been investigated in transplant patients. N-terminal pro-brain natriuretic peptide (NT-proBNP) has not been evaluated in pediatric transplant patients. The purpose of this pilot study was to evaluate the association of cTnT and NT-proBNP with AR in pediatric cardiac transplant patients.

Methods: Plasma was obtained at the time of EMB from pediatric patients ≥ 1 year old. N-terminal pro-brain natriuretic peptide was measured in fresh plasma at the time of biopsy, and cTnT was measured from frozen, stored samples using the highly sensitive assay for troponin T. Biomarker data were correlated with EMB results. Cellular AR was defined as an International Society for Heart and Lung Transplantation biopsy score of grade ≥ 2R.

Results: Fifty-three blood samples were obtained from 42 patients (mean age 11 years). Seven episodes of AR occurred in 5 patients. Biopsies with vs without AR were associated with higher cTnT (median [interquartile range {IQR}] 66 [45-139] vs 7 [2-13] pg/mL, P = .001) and NT-proBNP (median [IQR] 11,169 [280-23,317] vs 334 [160-650] pg/mL, P < .01). After successful treatment of AR in 5 patients, cTnT fell markedly (median [IQR] 53.5 [44.8-66.5] to 10.7 [1.5-16.4], P = .05).

Conclusion: In this pilot study, we found marked elevation of cTnT and NT-proBNP among children with AR. Moreover, reduction in cTnT levels after treatment paralleled improvement in EMB results. If these findings are confirmed in larger prospective studies, monitoring with these biomarkers may obviate surveillance EMB.