Three Years Outcome of Virtual Crossmatch Strategy in Heart Transplant Recipients

s S131 visits. A novel approach for quantifying dd-cfDNA using targeted amplification and next-generation sequencing was used to quantify dd-cfDNA on 109 plasma samples from these 24 patients. 3 to 10 samples were collected between 2 months and 1 year post-transplantation for each patient. Most plasma samples had endomyocardial biopsy rejection grades and geneexpression profiling (GEP) test scores available from the same clinic visits. Results: Median dd-cfDNA was 0.79% (interquartile range [0.38%, 1.30%]). Total between-patient variability (51% CV) was similar to within-patient variability (45% CV). Analytical variability was 17%. The ratio of betweenpatient variability to within-patient variability was 1.6 times lower for ddcfDNA than for GEP. No effect of recipient gender, age, CMV serologic status, or time post-transplantation was seen on % dd-cfDNA measurements. Conclusion: In this longitudinal study of non-rejecting heart transplant recipients, the withinand between-patient variabilities of dd-cfDNA were shown to be of similar size, and significantly larger than the analytical variability of the assay. The ratio of between-patient variability to within-patient variability was significantly less than in GEP, suggesting that dd-cfDNA does not depend as strongly on patient-specific factors as does GEP. dd-cfDNA showed no dependence on patient age, gender, CMV serologic status, or time since transplant in this cohort. Taken together, these characteristics indicate that dd-cfDNA is a stable analyte in non-rejecting patients. (Study sponsored by CareDx, Inc.)