An article by : Sílvia Casas1, Thierry Viard2, Curt Lind2
1 Medical Affairs, Laboratory Products, CareDx AB, Stockholm, Sweden; 2 Research and Development, Laboratory Products, CareDx Inc., CA, USA
CareDx is a global, 100% transplant focused company, demonstrating leadership in serving European laboratories, researchers, and clinicians with its state-of-the-art product portfolio of next-generation sequencing (NGS) based AlloSeq products, which serve as pre- and post-transplantation solutions.
For pre-transplant application, CareDx offers HLA typing solutions QTYPE and AlloSeq Tx. For post-transplantation monitoring, CareDx offers AlloSeq HCT chimerism testing and AlloSeq cfDNA for labs to measure the relative amount of donor derived cfDNA (dd-cfDNA) in solid organ transplant recipients. All products are CE marked. For research purposes, CareDx also provides AlloSeq Tx and AlloSeq cfDNA testing as services for customers who prefer to use the CareDx service lab in Stockholm, Sweden.
In solid organ transplant recipients, circulating donor-derived cell-free DNA (dd-cfDNA) is a biomarker of transplant allograft injury that may enable more frequent, quantitative, and safer assessment of allograft rejection and injury status. The addition of dd-cfDNA into routine transplant monitoring enables early detection of subclinical allograft rejection and immunosuppression intervention prior to development of clinically worsening allograft failure. Testing dd-cfDNA levels complements histology and clinical biochemical laboratory surveillance strategies as a prognostic marker and risk-stratification tool post-transplant. When considering personalized medicine, dd-cfDNA testing may help to identify allograft quiescence or absence of injury, thus supporting improved treatment decisions.
CareDx has developed AlloSeq cfDNA, a targeted NGS assay that relies on 202 single-nucleotide polymorphisms (SNPs) located throughout the genome to measure the dd-cfDNA in transplant recipients. The assay was designed to be fully compatible with any clinical laboratory setup and combines a streamlined workflow with a fully automated analysis software to accurately quantify dd-cfDNA in transplant recipients. The assay does not require prior genotyping of either the donor or recipient. The number of SNPs are statistically sufficient to distinguish between donor and recipient even when they are closely related genetically.
The assay includes a locus-specific oligonucleotide primer pool to amplify the targeted regions of interest and specifically designed index adapters to allow the unique cycling protocol to amplify the locus-specific regions and to index the libraries concurrently. Indexed samples are subsequently pooled and purified together to prepare for sequencing.
After sequencing is complete, the report generated by the AlloSeq cfDNA software provides the percentage of dd-cfDNA present in each sample, in less than 24 hours after blood sample processing. Library preparation is completed within 4 hours of which only 1-hour hands-on time (HOT). Multiple recipients can be analyzed in parallel and the AlloSeq cfDNA software design also allows monitoring %dd-cfDNA levels in the same recipient over time. The software can calculate % dd-cfDNA from multiple post-transplant samples and displays the results to compare levels of each sample to support longitudinal studies. Details of the analysis output is also available for each sample to access sample quality metrics, facilitating potential troubleshooting, and alignment with laboratory accreditation bodies.
This sensitive, minimally invasive, cost-effective sequencing assay requires low sample input, minimal HOT, and can provide results within 24 hours of obtaining recipients’ cfDNA. The assay can be performed in most clinical laboratories, providing a rapid turnaround time preferred in post transplantation surveillance.
AlloSeq cfDNA is a validated and certified assay that can be used to monitor for and detect allograft injury, and may enable better outcomes for transplant patients around the world.
AlloSeq cfDNA kit is CE-IVD in EU and the UK and Research Use Only (RUO) for the rest of the world. AlloSeq cfDNA is only available outside of the United States. For local regulatory status of AlloSeq products, please contact CareDx. Research Use Only products are not to be used for diagnostic procedures. AlloSeq is a trademark or registered trademark of CareDx Inc. or its subsidiaries in the US or other countries. AlloSeq is a registered trademark with the US Patent and Trademark Office.