S. K. Goh1,2, H. Do2,3, A. Testro6, J. Pavlovic6, A. Vago6, J. Lokan4, R. M. Jones1,5,6, C. Christophi1,5,6, A. Dobrovic1,2,3,7, V. Muralidharan1,5,6 1Department of Surgery, The University of Melbourne, Austin Health, Victoria, Australia 2Translational Genomics and Epigenomics Laboratory, Olivia Newton-John Cancer Research Institute, Victoria, Australia 3School of Cancer Medicine, La Trobe University, Victoria, Australia 4Department of Anatomical Pathology, Austin Health, Victoria, Australia 5Hepato-Pancreato-Biliary & Transplant Surgery Unit, Austin Health, Australia 6Victorian Liver Transplant Unit, Austin Health, Victoria, Australia 7Department of Clinical Pathology, The University of Melbourne, Victoria, Australia
Introduction: Assessment of donor-specific cell-free DNA (dscfDNA) in the recipient is emerging as a non-invasive biomarker of organ rejection after transplantation. We previously developed a digital PCR-based approach that readily measures dscfDNA within clinically relevant turnaround times. Using this approach, we characterised the dynamics and evaluated the clinical utility of dscfDNA after liver transplantation (LT).
Methods: Deletion/insertion polymorphisms (DIPs) were used to distinguish donor-specific DNA from recipient-specific DNA. Post-transplant dscfDNA was measured in the plasma of the recipients. In the longitudinal cohort, dscfDNA was serially measured at days 3, 7, 14, 28 and 42 in 20 recipients. In the cross-sectional cohort, dscfDNA was measured in four clinically stable recipients (>1-year post-transplant) and 16 recipients (>1-month post-transplant) who were undergoing liver biopsies.
Results: Recipients who underwent LT without complications demonstrated an exponential decline in dscfDNA. Median levels at days 3, 7, 14, 28 and 42 were 1936, 1015, 247, 90 and 66 copies/mL respectively. dscfDNA was higher in recipients with treated biopsy-proven acute rejection (tBPAR) as compared to those without. The area under the receiver operator characteristic curve of dscfDNA was higher compared to that of liver function tests for tBPAR (dscfDNA:98.8% with 95%CI of 95.8-100%, ALT:85.7%, ALP:66.4%, GGT:80.1% and bilirubin:35.4%).
Conclusion: dscfDNA as measured by probe-free droplet digital PCR methodology was reflective of organ integrity after LT. Our findings affirmed the promising utility of dscfDNA as a promising diagnostic tool of tBPAR.