A Sensitive Cardiac Troponin I Assay to Screen for Acute Rejection in Heart Transplant Patients
How good is the novel highly sensitive (hs) cardiac troponin I (cTnI) assay for detecting acute rejection after orthotopic heart transplant (OHT)?
The study investigators matched stored serum samples to endomyocardial biopsies (EMBs) in 98 recipients of OHT who survived ≥3 months post-transplant. They defined acute rejection (AR) as ISHLT grade 2R or higher cellular rejection, acellular rejection, or allograft dysfunction of uncertain etiology leading to treatment for presumed rejection; hs assay was used to measure cTnI. They utilized cross-sectional analyses to determine the association of cTnI concentrations with rejection and ISHLT grade, and the performance metrics of cTnI for the detection of AR.
The investigators found that among the 98 subjects, 37% had at least one rejection episode. cTnI was measured in 418 serum samples, including 35 paired to a rejection episode. In this cohort, cTnI concentrations were significantly higher in rejection versus non-rejection samples (median 57.1 vs. 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). When they utilized a cut-point of 15 ng/L, they found that sensitivity of this assay was 94%, specificity 60%, positive predictive value 18%, and negative predictive value 99%.
The authors concluded that hs-cTnI assay appears useful to “rule out” AR in recipients of OHT.
The findings of this study are important because the high negative predictive value of this assay makes it a powerful tool in rapidly excluding AR. Prospective larger studies are needed to validate the findings of this study. If these findings are validated, then potentially this assay may decrease utilization of gene profiling or EMBs for routine surveillance. The other advantage of this assay is that potentially it could be performed at point of service, unlike EMB.
Keywords: Troponin I, Cross-Sectional Studies, Heart Failure, Transplantation, Homologous, Heart Transplantation
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