Donor-derived cell-free DNA in combination with liver function tests for biopsy decision-making in pediatric liver transplantation.

Surveillance biopsy is essential to detect graft rejection that remains silent to conventional liver function tests (LFTs), allowing tailored immunosuppression. The benefit of detecting subclinical biopsy-proven acute rejection (BPAR) comes at the cost of subjecting all pediatric recipients to an invasive procedure, including those who could potentially be safely spared if accurately identified as low risk of rejection using sensitive and noninvasive biomarkers of graft injury. We evaluated the ability of donor-derived cell-free DNA (dd-cfDNA) to rule out BPAR in pediatric liver transplant (LT) patients and its role in biopsy decision-making when used alongside LFTs. A clinical decision-making process combining LFTs and dd-cfDNA to identify low-risk rejection patients was developed using data from 98 patients under surveillance and 40 patients who underwent for-cause biopsy. Sixty BPAR events were recorded, and almost half of them (46.7%) were classified as subclinical BPAR (subBPAR). Only dd-cfDNA distinguished subBPAR from BPAR-free cases ( p =0.02), demonstrating a sensitivity of 96.7% (95% CI, 88.6-99.4) and a specificity of 34.6% (95% CI, 25.0-45.7) at a threshold of 1.9%. According to the decision-making process, patients with LFTs below the upper limit of normal and dd-cfDNA <1.9% would be spared from liver biopsy. Considering a BPAR prevalence of 43.4% in the study cohort, the negative and positive predictive values were 93.1% and 53.2%, respectively. In this large pediatric study, we demonstrate for the first time that low dd-cfDNA levels can reliably identify liver transplant patients at low risk of rejection, improving the tailoring of surveillance biopsies when used alongside LFTs.