# Donor-derived cell-free DNA testing in pediatric kidney transplant recipients: indications and clinical utility

## TL;DR

This study shows that donor-derived cell-free DNA testing can help detect rejection and antibodies in pediatric kidney transplant patients without the need for biopsies.

## Contribution

The study demonstrates the clinical utility of dd-cfDNA testing in pediatric kidney transplant recipients for non-invasive monitoring.

## Key findings

- Elevated dd-cfDNA is strongly associated with biopsy-proven acute rejection and de novo anti-HLA antibodies.
- Low dd-cfDNA levels are observed in patients with no signs of rejection or antibodies.
- Patients with DQ and DR dnHLAab and donor-specific antibodies are more likely to have elevated dd-cfDNA.

## Abstract

We describe our single-center experience in performing donor-derived cell-free DNA (dd-cfDNA) testing for a clinical indication in pediatric kidney transplant recipients.

Dd-cfDNA was done for increase in creatinine, appearance of de novo anti-HLA antibodies (dnHLAab) and for a clinical indication. We compared clinical characteristics of patients with dd-cfDNA > 1 with those with dd-cfDNA ≤ 1 and also compared dd-cfDNA in patients with no biopsy proven rejection (BPAR) or dnHLAab with those with BPAR, and those with dnHLAab and no BPAR.

Chart review was performed in 106 patients with a mean age of 11.0 ± 5.5 years. When compared with 62 patients with dd-cfDNA ≤ 1, 59.0% (26/44) of patients with dd-cfDNA > 1 had BPAR (OR 13.5: 95%CI 4.6,38; p < 0.0001), and 88.1% (37/44) had dnHLAab (OR 60.3 95%CI 17.2,192.2; p < 0.0001). Patients with DQ and DR dnHLAab (OR 115.2: 95%CI 24.8, 509.5; p < 0.0001) and those with donor-specific antibodies (DSAs) (OR 50.8: 95%CI 13.0, 168.7; p < 0.0001) were likely to have dd-cfDNA > 1. A repeated measures linear mixed effect model revealed a significant difference in dd-cfDNA between those with no antibodies or BPAR (p < 0.0001) and patients with BPAR and dnHLAab, with or without DSA. At the end of the follow-up period, eGFR was 72 mL/min/1.73 m2 in those without BPAR or dnHLAab and was significantly different from those with BPAR (eGFR 51 mL/min/1.73 m2 (p < 0.0001).

Elevated dd-cfDNA is strongly associated with BPAR, class II dnHLAab and DSAs. Conversely, low values are observed in immunoquiescent states. Dd-cfDNA can be a useful tool for non-invasive clinical decision-making.

A higher resolution version of the Graphical abstract is available as Supplementary information

A higher resolution version of the Graphical abstract is available as Supplementary information

The online version contains supplementary material available at 10.1007/s00467-025-06770-w.