Biological Variation Of Donor-Derived Cell-Free Dna In Lung Transplant Recipients

Purpose Prior studies have demonstrated that percentage donor-derived cell-free DNA (%dd-cfDNA) in lung transplant patients may serve as a noninvasive marker of allograft injury and aid in the detection of acute allograft rejection, infection and chronic lung allograft dysfunction (CLAD). Clinical interpretation of %dd-cfDNA values require an understanding of its normal biological variation in stable lung transplant patients in order to identify abnormal results that may indicate the presence of allograft dysfunction. This study establishes the biological variation and reference change values (RCV) of %dd-cfDNA in lung transplant patients using an analytically validated assay with an established analytic coefficient of variation (CVA) of 6.8%. Methods Levels of plasma %dd-cfDNA (Allosure®) were analyzed from a cohort of patients at 4 lung transplant centers using %ddcfDNA as a method to monitor for allograft rejection in place of surveillance transbronchial biopsy. Patients with stable allograft function and ≥ 3 %dd-cfDNA samples were included. Stable patients were defined as having no evidence of infection, rejection, symptoms or documented decline in forced expiratory volume in 1 second (FEV1) \u003e 10% from baseline. The AlloSure assay, a next-generation sequencing-based approach, was used to measure %dd-cfDNA in the plasma. Intraindividual coefficient of variation (CVI), interindividual CV (CVG), the index of individuality (II) and the RCV were calculated. Results 35 patients with a combined 124 %dd-cfDNA samples were included in the final analysis. 57% were men, the mean age was 59 years and 77% had bilateral lung transplants. The median %dd-cfDNA was 0.31% (interquartile range 0.18% - 0.68%), the 97.5th percentile and 95th percentile were 1.3% and 1.0% respectively. In 30 patients with an average of 3.7 tests, the CVI was 25%, the CVG was 19%, the II was 1.3 and the RCV was 72%. Conclusion In stable lung transplant patients, fluctuations in %dd-cfDNA levels of up 72% or levels less than 1% are within normal biological variation. With further validation, these thresholds may be incorporated into surveillance monitoring algorithms to identify potentially abnormal results indicating allograft dysfunction.