Surveillance after lung transplantation (LT) is critical to the detection of acute cellular rejection (ACR) and prevention of Chronic Lung Allograft Dysfunction (CLAD). Therefore, we measured donor-derived cell-free DNA (dd-cfDNA) implementing a clinical-grade, next generation targeted sequencing assay in 107 plasma samples from 38 unique LT recipients with diagnostic cohorts classified as: (1) Biopsy-confirmed or treated acute cellular rejection (ACR), (2) antibody-mediated rejection (AMR), (3) Obstructive chronic lung allograft dysfunction (CLAD), (4) allograft infection (INFXN), and (5) Stable healthy allografts (STABLE). Our principal findings: (1) dd-cfDNA level was elevated in ACR (median 0.91%; IQR: 0.39–2.07%), CLAD (2.06%; IQR: 0.57–3.67%), and an aggregated cohort of rejection encompassing allograft injury (1.06%; IQR :0.38–2.51%), compared with the STABLE cohort (0.38%; IQR: 0.23–0.87%) (p=0.02). (2) dd-cfDNA level with AMR was elevated (1.34%; IQR: 0.34–2.40%) compared to STABLE although did not reach statistical significance (p=0.07) due to limitations in sample size. (3) No difference in dd-cfDNA for allograft INFXN (0.39%; IQR: 0.18–0.67%) versus STABLE, that may relate to differences in “tissue injury” with spectrum of bronchial colonisation versus invasive infection. (4) No difference for dd-cfDNA in unilateral versus bilateral LT. (5) “Optimal Threshold” for dd-cfDNA for aggregated rejection events representing allograft injury was determined as 0.85%, with Sensitivity=55.6%, Specificity=75.8%, Positive Predictive Value (PPV)=43.3%, and Negative Predictive Value (NPV)=83.6%. Measurement of plasma dd-cfDNA may be a clinically useful tool for the assessment of lung allograft health and surveillance for “tissue injury” with a spectrum of rejection.
Plasma Donor-derived Cell-free DNA Levels Are Increased During Acute Cellular Rejection After Lung Transplant