With access to genetic testing becoming increasingly easier and the role of genetics in ALS becoming clearer, the demand for presymptomatic testing has increased.1,2

If a patient is diagnosed with ALS, and a mutation is identified, family members may want to have predictive genetic testing done to find out whether they also have the mutated gene. (Presymptomatic genetic testing by family members makes sense only when a genetic change has been identified in the person with ALS or if there is family history of the disease.3.)

Genetic testing merely establishes that a person has one of the discovered mutated genes associated with the disease. It doesn’t predict whether they will get the disease, and it does not provide a diagnosis. Moreover, because of the complexity of the genes involved, the findings may be unclear.4


What is Predictive and Presymptomatic Testing?

How does predictive genetic testing work? Predictive genetic testing can spot mutations that will increase a person’s risk of developing inherited genetic diseases, especially certain forms of cancer. Presymptomatic testing determines if the person will eventually have a genetic disorder prior to any symptoms showing up.


Weighing the options of genetic testing

The choice to have presymptomatic genetic testing is deeply personal. Someone may pursue it out of a desire to resolve the uncertainty of whether they carry the gene and perhaps to inform family-planning decisions. Some may opt for the testing so they can learn their genetic status for clinical trial participation and/or to help advance research.5

But it’s a weighty decision with both intended and unintended consequences:

  • The burden of knowledge: Even when the family member truly wants to know their status, it can be difficult to live with the knowledge of a possible impending illness.
  • Family conflict: Members of the same family may disagree about wanting to know if they carry the mutation, and there’s always the possibility someone who gets tested may inadvertently reveal their status to a family member who didn’t want to know.6,7
  • Cost: Testing for all currently known ALS genes can cost from $1,600 to $5,000. Checking for one known gene can cost about $400, according to the ALS Association. Depending on the insurance company, patients may need to pay out of pocket.8
  • Privacy: The findings may not remain private. GINA, the Genetic Information Nondiscrimination Act of 2008, was enacted to protect people from genetic discrimination in health insurance and employment. Protected information would include a family history of ALS and a positive genetic test result. However, GINA doesn’t apply when an employer has fewer than 15 employees, nor does it apply to other types of insurance (e.g., disability and long-term care).9


The role of the genetic counselor

With so many factors to consider, genetic counseling is recommended — and often required — for presymptomatic testing. Meeting with a genetic counselor involves taking a detailed medical and family history, evaluating risks, and discussing the implications of such testing. Genetic counseling does not always lead to genetic testing; sometimes, it leads a person to decide against it.10

The genetic landscape of ALS is complex, continually changing, and not fully understood. 11 Being able to sit with that uncertainty is a prerequisite to presymptomatic testing.


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  1. Amador MDM, Gargiulo M, Boucher C, et al. Who and Why? Requests for Presymptomatic Genetic Testing for Amyotrophic Lateral Sclerosis/Frontotemporal Dementia vs Huntington Disease. Neurol Genet. 2020;7(1):e538. Published 2020 Dec 24. doi:10.1212/NXG.0000000000000538
  2. Corcia P, et al. on Behalf the FILSLAN network. Pre-symptomatic diagnosis in ALS. Rev Neurol (Paris). 2020 Mar;176(3):166-169. doi: 10.1016/j.neurol.2019.07.027. Epub 2020 Jan 10. PMID: 31932031.
  3. Genetic Testing for ALS, ALS Association https://www.als.org/understanding-als/who-gets-als/genetic-testing
  4. Fanos, J., Gronka, S., Wuu, J. et al. Impact of presymptomatic genetic testing for familial amyotrophic lateral sclerosis. Genet Med 13, 342–348 (2011). https://doi.org/10.1097/GIM.0b013e318204d004
  5. Benatar M, Stanislaw C, Reyes E, et al. Presymptomatic ALS genetic counseling and testing: Experience and recommendations. Neurology. 2016;86(24):2295-2302. doi:10.1212/WNL.0000000000002773
  6. Mendes Á, Paneque M, Clarke A, Sequeiros J. Choosing not to know: accounts of non-engagement with pre-symptomatic testing for Machado-Joseph disease. Eur J Hum Genet. 2019;27(3):353-359. doi:10.1038/s41431-018-0308-y
  7. What are the risks and limitations of genetic testing? https://medlineplus.gov/genetics/understanding/testing/riskslimitations/
  8. Genetic Testing for ALS. ALS Association https://www.als.org/understanding-als/who-gets-als/genetic-testing
  9. What is genetic discrimination? MedlinePlus https://medlineplus.gov/genetics/understanding/testing/discrimination/
  10. Familial Amyotrophic Lateral Sclerosis (FALS) and Genetic Testing https://www.als.org/navigating-als/resources/familial-amyotrophic-lateral-sclerosis-fals-and-genetic
  11. Benatar M, Stanislaw C, Reyes E, et al. Presymptomatic ALS genetic counseling and testing: Experience and recommendations. Neurology. 2016;86(24):2295-2302. doi:10.1212/WNL.0000000000002773

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