Donor-derived Cell-free DNA: Advanced Biomarkers for Enhanced Kidney Recipient Surveillance

Dear Editor, In India, renal transplantation is the preferred treatment for individuals with end-stage renal disease (ESRD). India's living renal transplantation program, the second largest globally after the USA, has evolved significantly over 45 years.[1] However, one of the significant obstacles encountered during transplant procedures is the occurrence of transplant rejection. Monitoring the health and function of transplanted kidneys is paramount for ensuring the well-being of kidney transplant recipients. Current methodologies employed for this purpose, such as measuring plasma creatinine levels, monitoring immunosuppressive drug levels, assessing proteinuria and hematuria, examining donor-specific antibodies (DSAs), and employing duplex ultrasonography, present certain diagnostic limitations.[2,3] Consequently, there is a pressing need for more effective biomarkers that can provide actionable insights into early detection or exclusion of rejection, asymptomatic graft injury, and the adequacy of immunosuppressive therapy. This is an attempt to delve into the promising role of donor-derived cell-free DNA (dd-cfDNA) as an innovative biomarker for monitoring graft integrity and facilitating the detection or exclusion of rejection, supported by robust clinical evidence from numerous published studies. The existing approaches for kidney recipient surveillance have their inherent shortcomings, which hinder their ability to provide comprehensive and reliable information. Plasma creatinine levels, while commonly used, are insensitive to early graft dysfunction and may not manifest until substantial damage has occurred. Monitoring immunosuppressive drug levels, while crucial, fails to offer a complete picture of graft status and may not reflect subclinical rejection episodes. Proteinuria and hematuria, though indicative of graft issues, lack specificity and may not always signify rejection. Evaluating DSA and employing duplex ultrasonography, although valuable tools, may not yield timely and definitive insights into graft health.[2] In the quest for improved kidney recipient surveillance, dd-cfDNA has emerged as a promising biomarker. Dd-cfDNA represents the genetic material from the transplanted organ that circulates in the recipient's bloodstream. It offers several advantages over traditional methods. First, dd-cfDNA can detect graft injury early, even before clinical symptoms or changes in creatinine levels become apparent. This early detection capability is crucial for timely intervention and preserving graft function. Moreover, dd-cfDNA can aid in the exclusion or detection of rejection episodes, providing valuable guidance to clinicians in tailoring immunosuppressive therapies. By monitoring the levels of dd-cfDNA, health-care providers can distinguish between immune-mediated rejection, nonimmune-mediated injury, and stable graft function, allowing for a more precise diagnosis and treatment strategy.[4] The adoption of dd-cfDNA as a valuable tool in kidney recipient surveillance is supported by an extensive body of clinical evidence. Numerous published studies have demonstrated its efficacy in assessing graft integrity and detecting or excluding rejection episodes. These studies have shown that dd-cfDNA levels correlate with the severity of graft injury, making it a reliable marker for monitoring transplant outcomes. In conclusion, current approaches for kidney recipient surveillance possess inherent limitations that hinder their ability to provide comprehensive and early insights into graft health. However, the integration of dd-cfDNA as a biomarker offers a promising solution to these challenges. With its capacity to detect graft injury early and provide guidance on rejection episodes, dd-cfDNA represents a valuable addition to the transplant monitoring toolkit. The substantial clinical evidence supporting its efficacy underscores the potential of dd-cfDNA to enhance the care and outcomes of kidney transplant recipients. Currently, two concurrent approaches exist for employing dd-cfDNA as biomarkers. These involve assessing the quantity of donor molecules through either next generation sequencing or the digital PCR method. In contrast to the droplet digital method utilized by Beck et al., the next-generation sequencing method employs a panel of 266 SNPs, while the droplet digital method uses 41 SNPs. Despite the differences in SNP panels, both methodologies yield equivalent results.[3,5] India has witnessed a substantial increase in the number of renal transplantations over the years, primarily due to the rising burden of ESRD and increased awareness about organ donation.[1] In light of these trends, it becomes crucial to explore and invest in technologies like dd-cfDNA testing as part of the posttransplant management protocol. While the initial costs may be daunting, the long-term benefits of early rejection detection, reduced reliance on invasive procedures, and improved patient outcomes cannot be overstated. Moreover, as technology advances and competition in the diagnostic market grows, there is a potential for cost reductions over time. Collaborations between health-care institutions, research organizations, and industry partners can also play a role in making dd-cfDNA testing more accessible and affordable in the Indian health-care setting. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.