Absolute quantification of donor-derived cell-free DNA following pediatric and adult heart transplantation.

OBJECTIVE

Traditional rejection surveillance after heart transplantation (HTx) is based on endomyocardial biopsies (EMBs), which are invasive, expensive, and associated with complications. Monitoring using cell-free DNA (cfDNA) is promising, but most studies report only on the donor fraction (DF) as the percentage of donor-derived cfDNA (dd-cfDNA) relative to total cfDNA. We evaluated the performance of dd-cfDNA to detect rejection.

METHODS

HTx patients were prospectively enrolled in a multicenter study, and blood samples were collected concurrently with EMB. Dd-cfDNA was quantified using droplet digital PCR (ddPCR). Rejection was defined by EMB results and compared to nonrejection EMB. Patients with symptomatic rejection were studied as a subgroup, and test performance was determined using receiver operation characteristic analysis.

RESULTS

We included 94 patients (70 adults and 24 children), which resulted in 1007 EMB and blood samples. In 19 patients, there were 32 rejection episodes >14 days past HTx, with 15 of them being symptomatic. In receiver operation characteristic analysis, dd-cfDNA and DF could discriminate quiescence from rejection with an area under the curve (AUC) of 0.68 and 0.65, respectively. Dd-cDNA at a threshold of 25 copies/ml showed an AUC of 0.87 to detect symptomatic rejection, significantly better than DF (AUC of 0.75).

CONCLUSIONS

dd-cfDNA found good discrimination between cardiac recipients with and without rejection. Absolute quantification of dd-cfDNA with ddPCR is a fast and effective method to monitor graft health. Analyzing absolute dd-cfDNA levels helps identify other factors, besides rejection, that may influence cfDNA levels, potentially reducing the need for EMB.