A Prospective Pilot Study to Investigate Whether Donor‐Derived Cell‐Free DNA Can Be Used as a Biomarker of Recurrent IgA Nephropathy Post–Kidney Transplantation

IgA nephropathy (IgAN) is one of the most prevalent glomerulonephropathies and commonly leads to kidney failure. The recurrence of IgAN following transplantation remains a significant concern. Currently, detecting IgAN recurrence requires a kidney biopsy, highlighting the need for non-invasive biomarkers such as donor-derived cell-free DNA (dd-cfDNA) to aid in early detection. This prospective pilot study aims to evaluate dd-cfDNA as a non-invasive biomarker for detecting IgAN recurrence post-kidney transplantation. Specifically, the study seeks to compare %dd-cfDNA levels in transplanted patients with and without IgAN recurrence and correlate these levels with other kidney function parameters. A total of 32 patients with histologically confirmed IgAN were enrolled, including those with documented IgAN recurrence post-transplantation and those without recurrence. Plasma samples were collected and processed using the AlloSeq cfDNA kit to quantify relative %dd-cfDNA levels. Kidney function parameters, including estimated glomerular filtration rate (eGFR) and proteinuria, were also assessed. The study found no significant difference in %dd-cfDNA levels between transplanted patients with IgAN recurrence and those without recurrence (median 0.37% [IQR 0.28%-3.53%] vs. median 0.42% [IQR 0.15%-0.84%], p = 0.67). Also, %dd-cfDNA (AUC = 0.57 [95% CI 0.28-0.85], p = 0.64) failed to effectively discriminate IgAN recurrence compared to traditional kidney function parameters such as proteinuria (AUC = 0.96 [95% CI 0.87-1.00], p = 0.002) and eGFR (AUC = 0.74 [95% CI 0.47-1.00], p = 0.09). Relative (%) dd-cfDNA alone may not be a robust biomarker for detecting IgAN recurrence post-transplantation. While proteinuria proved a more effective indicator in this study, kidney biopsy remains the gold standard for definitive diagnosis. These findings highlight the challenges of using %dd-cfDNA as a standalone diagnostic tool for monitoring IgAN recurrence post-transplantation. Future research should explore larger patient cohorts and longitudinal assessments to refine the utility of dd-cfDNA and investigate potential combination strategies with other biomarkers.