A two-threshold donor-derived cell-free DNA algorithm improves detection of molecular rejection in heart...

Donor-derived cell-free DNA (dd-cfDNA), a noninvasive biomarker for heart allograft rejection, was initially developed based on the percent of total cfDNA. A two-threshold algorithm (2TA) was recently developed, assigning high risk of rejection if dd-cfDNA was ≥0.26% or donor-quantity score (DQS) was ≥18 copies/mL based on histologic biopsy assessment. The present study evaluated 2TA for its performance in detecting molecular rejection using the Molecular Microscope Diagnostic System (MMDx).

We assessed endomyocardial biopsies with matched dd-cfDNA assessments from the multicenter, prospective Trifecta-Heart study (ClinicalTrials.gov, NCT04707872).

Among 366 biopsy-matched samples from 236 patients, MMDx classified 108 biopsies as rejection and 258 as no rejection. Median dd-cfDNA% and DQS were significantly higher in rejection vs non-rejection (0.67% vs 0.07%; 44 vs 1 copies/mL; p<0.001 for both) and were higher in antibody-mediated, T cell-mediated, and mixed rejection. Compared to the previous 0.15% dd-cfDNA cutoff, 2TA provided higher specificity (83.7% vs 76.7%) but similar sensitivity (83.3% vs 82.4%), reducing false positives by 30% with AUC of 0.87, a net reclassification index of 7.23%, and detecting molecular rejection better than histologic rejection. Each 0.05% increase in dd-cfDNA% and 5-copy/ml increase in DQS raised the odds of MMDx rejection by 14% and 20%, respectively.

Using dd-cfDNA% with DQS for heart transplant rejection improves specificity and AUC compared to the previous cutoff, predicting molecular rejection better than histologic rejection.