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Chimerism Testing

Chimerism testing (engraftment analysis) is performed for patients who have received a hematopoietic stem cell transplant. The test involves identifying the genetic profiles of the recipient and of the donor and then evaluating the extent of mixture in the recipient’s blood or bone marrow. First, DNA is isolated from the recipient and potential donor before the transplant and analysis is performed to determine whether the genetic markers unique to the donor and the recipient have sufficient power to distinguish the donor from the recipient. Next, after the transplant takes place, the performance of the transplant engraftment is assessed by evaluating the donor versus recipient contribution of white blood cells in post-transplant blood or bone marrow specimens obtained from the recipient.

  • The DNA is isolated from the recipient, donor, and post-transplant samples.
  • DNA is amplified via the Promega GenePrint24 System which employs methodology commonly used in human identity testing and is accomplished by the analysis of genomic polymorphisms called short tandem repeat (STR) loci.
  • The percent donor chimerism is calculated and reported, and a longitudinal plot of historic data is generated for successive post-transplant specimens.

Exome Sequencing

  • CES is a test that examines the portion of the genome that encodes for proteins (exons) and their flanking splice junctions.
  • CES aims to identify disease-causing variants within the exons.
  • CES interprets the identified variants within the context of the clinical presentation in order to reach a diagnosis for patients with challenging undiagnosed genetic disorders.
  • The UAGC-CS sequences full trio or proband-only exomes encompassing over 50MB of around 21,000 human genes.
  • Patients are sequenced to a depth greater than 50X coverage on a Illumina HiSeq 2500 and all data is aligned and mapped back to the human reference genome.
  • The UAGC-CS clinical report includes all validated de novo variants as well as alternate alleles found in the patient sample prioritized by known or potential pathogenicity and relation to the clinical phenotype.
  • Incidental findings are also reported if patient is consented to receive such findings.
  • Genetic counseling before and after testing is required.