Welcome back to the OAGC monthly blog! We are starting the new year with information about DNA banking! Have you ever wondered why you might discuss DNA banking with a family? Maybe you want to know what labs are available for DNA banking? Or how much testing can be completed from a banked sample? Cara Barnett explores all this, and more, in her post. Happy reading (and Happy New Year)!
What is DNA Banking?
DNA banking is the storage of DNA for future use, and is offered by many clinical genetics laboratories. It is available on many sample types including blood, saliva, and sometimes, blood spot cards. For sample types such as blood and saliva, laboratories can obtain between 100-200 micrograms of DNA, and for most next generation sequencing based testing only 5 micrograms is required, providing the opportunity for multiple rounds of genetic testing. The amount of DNA obtained from other tissue types is extremely variable, and enough DNA may only be obtained for one round of genetic testing. While many diagnostic genetic testing laboratories store DNA in association with quality control protocols, these samples are not held indefinitely and relying on extra sample availability from a diagnostic laboratory is not a guarantee.
At the time of this post, DNA banking is commercially available at the cost of $169 for 50 years of secure and confidential storage. A list of all laboratories offering DNA banking is available through the NIH genetic testing registry and can be found by clicking here.
Additionally, many research studies bank DNA to use in future gene-hunting or segregation analysis proposals.
Why bank DNA?
Genetic counseling is a fast growing field that continues to expand into many areas of medicine, such as public health, public policy, and technology. At this time, the majority of genetic counselors are involved in clinical practice and ordering genetic testing for patients with a personal or family history suggestive of a genetic disease. Irrespective of the specific area of clinical practice, or indication for genetic testing, there are always patients left without clear answers. What happens when genetic testing is unable to find an answer for someone with a personal or family history of genetic disease? This scenario, among many others, is when DNA banking should be considered.
DNA Banking in Practice
Genetic counselors within cardiology commonly discuss DNA banking when working with families who have recently lost a loved one to sudden death and are interested in postmortem genetic testing. DNA banking prior to postmortem genetic testing is an essential discussion to have with families, especially if there is only one sample available. In cases of sudden unexplained death, there is approximately a 15-30% chance of identifying a disease causing variant in a cardiomyopathy or arrhythmia gene. Many families find the opportunity to store DNA appealing, as DNA banking may provide future opportunities to identify the cause of their loved ones’ sudden death.
Another scenario in which DNA banking is often considered is for those with undiagnosed diseases. In the setting of fetal and pediatric cases, adult onset cases, and even familial cancer cases without an identifiable genetic cause, DNA banking may provide opportunities for family and loved ones to pursue answers at a later time. Accessing stored DNA provides the ability to pursue additional genetic testing in the future after new genes have been discovered, even after a family member dies. These opportunities increase the potential to identify answers for these families. Identifying the answer for a previously undiagnosed disease in a family may refine recurrence risk information, identify at-risk relatives, and provide psychological relief and the end to a diagnostic odyssey.
In the space of reproductive genetics, DNA banking may be vital for families interested in preimplantation genetic testing for monogenic disease (PGT-M). PGT-M allows for the selection of embryos that do not carry the monogenic disease that runs in the family. Individuals may seek PGT-M for diseases such as cystic fibrosis, Fragile X syndrome, Duchenne muscular dystrophy, neurofibromatosis, Huntington’s disease, or hereditary cancer syndromes. Currently, PGT-M is completed via linkage analysis. While some cases may be able to proceed without family member references, some require DNA from two generations of affected individuals. DNA banking for an affected loved one may provide future family members the ability to pursue PGT-M when it may have otherwise been impossible.
Take Home Message
DNA banking is a resource that should be in the tool belt of all genetic counselors, in both clinical and non-clinical roles. A genetic counseling session is an appropriate environment to discuss DNA banking with families, as the empowerment and opportunities DNA banking provides families is complementary to the goals of the genetic counseling session.