Evaluating the Diagnostic Utility of dd-cfDNA in Renal Allograft Surveillance: A Single-Center Perspective

<b>Background:</b> Donor-derived cell-free DNA (dd-cfDNA) testing offers a non-invasive approach for monitoring allograft health in transplant recipients. However, its diagnostic performance and clinical utility remain insufficiently characterized across diverse populations. <b>Objectives:</b> This study assesses concordance between dd-cfDNA, donor-specific antibody (DSA) testing, and biopsy, while also comparing two commercial assays (AlloSure and Prospera) in kidney and pancreas transplant recipients. <b>Methods:</b> We retrospectively analyzed 271 transplant patient records from 2019 to 2024 at our institution, focusing on dd-cfDNA testing. Statistical analyses evaluated assay performance in relation to DSA and biopsy results. The impact of multi-organ transplantation (MOT) on dd-cfDNA levels was also assessed. <b>Results:</b> In our predominantly Caucasian cohort (61.5%) with a mean age of 53 years, increased levels of dd-cfDNA were significantly associated with DSA positivity, particularly within the Prospera group (<i>p</i> = 0.002), and were particularly higher in patients with HLA class II DSA. Both assays showed a limited correlation with biopsy-confirmed rejection. AlloSure had high specificity (80%) but low sensitivity (19%), whereas Prospera showed higher sensitivity (75%) with moderate specificity (60%). Dd-cfDNA levels were elevated in MOT recipients in a vendor-dependent manner. <b>Conclusions:</b> Our findings highlight the differing clinical strengths of dd-cfDNA assays: AlloSure demonstrates greater preference for ruling out rejection, whereas Prospera appears better suited for early detection. Dd-cfDNA interpretation in MOT recipients warrants cautious consideration. Overall, tailoring assay selection and optimizing diagnostic thresholds to clinical context may enhance transplant surveillance and patient management strategies.