Genomic Sequencing – Right Test at the Right Time

29 January, 2021 by genomics

If you are reading this, it is likely that you are curious about genomic sequencing and how it may benefit you or a family member with an undiagnosed condition. Genomic sequencing, although a powerful tool, is not always the most appropriate test to find a diagnosis. Here, we describe when genomic sequencing is most useful, what your doctor considers before suggesting this test to you, and what benefits and risks it can lead to as a patient.

What is genomic sequencing?

 Your genome is all your genetic material (i.e. DNA) found in every cell of your body.

The genome is made up of a four-letter chemical code. These chemical letters are A, T, C and G. Your entire genomic code contains 6 billion letters in total. The specific sequence of these letters is important for the normal functioning of your body.

Genomic sequencing is a process that involves ‘spelling out’ your entire genetic code to identify if there are any variants (i.e. genetic changes) that may explain your symptoms. However, this is difficult as we all have many variants in our genomes. Most of these are harmless (or benign), which means they do not cause any change in normal bodily functions. Therefore, genetic specialists will filter out these benign variants and focus on the ones they think are most likely to be the cause of symptoms.

What factors does your doctor consider before suggesting genomic sequencing?

 Genomic sequencing does not always identify the genetic cause of a condition. It is only offered if you have a set of symptoms that is not specific to a certain condition, and other tests have not found a diagnosis. This type of testing may also be offered if you are part of a research study or clinical trial.

Your doctor will consider:

  • How likely it is that your symptoms are being caused by a single gene rather than an interaction between multiple genes;
  • If it is already obvious what condition you have without a genetic diagnosis (therefore, it is unlikely a genomic sequencing test will change your treatment or management plan further);
  • If another type of genetic test is more appropriate; or
  • The cost of the test (i.e. tests other than genomic sequencing may be Medicare-rebated or cheaper, and therefore more appropriate).
What are the benefits associated with genomic sequencing?

 Benefits associated with genomic sequencing may include:

  • If a diagnosis is made you have a name for the condition;
  • Being able to give this diagnosis to your GP, which means they will be able to inform themselves of the condition and provide you with more appropriate healthcare services in the future;
  • Feeling relief even if there is no treatment or cure available;
  • Feeling relief as you no longer have to go through many different tests to find a diagnosis;
  • You may have a change in medical management and treatment strategies more specific to your condition; and
  • Family members may be tested for the genetic variant causing your condition for family planning or other purposes.

Even if a diagnosis is not made, benefits may include:

  • Other conditions can be ruled out; and
  • Your genomic information may be re-analysed in future when new genetic discoveries are made
What are the risks associated with genomic sequencing?

Because genomic sequencing produces so much data, there is a chance you may receive some uncertain results. These are called variants of unknown significance (VUS) and it is not known whether they do or do not contribute to the development of your condition. However, these are usually not reported. Future research on VUS results may confirm whether it is causing disease. In this case, your results may be looked at again.

There may also be an incidental finding, where a variant is found in a gene that contributes to a different condition. However, testing laboratories will aim to limit the chance of ‘seeing’ these kinds of results. How would you feel if you were to receive these unwanted or unforeseen findings?

It is also important to remember that any genomic information you find about yourself will also impact your biological family members. Do your family members want to know if they are at risk of a certain condition? How will they take this news? Are you prepared to tell them your results if you have to?

Your ability to get affordable life insurance may also be influenced by your genomic data depending on your results. This could also impact other family members, as you share genomic information.

What are the limitations associated with genomic sequencing?

 There are still genetic causes of conditions that have not been discovered yet. This means that the results you receive from a genetic test will depend on what genetic information is currently known. However, this will change with more research. If this is the case, your genomic information may be looked at again in future to see if the genetic cause can be found.

You must provide consent for your genome to be sequenced and to receive the results. Doctors and genetic counsellors will be there to provide information throughout this process if testing is offered to you, but it is ultimately your choice whether you undergo testing.

Genomic sequencing will not give you answers to every single health concern you will ever have, or tell you about your risk of developing all other conditions. It is used in very specific circumstances to find a diagnosis for conditions where a cause cannot be found through other means of testing.

 

Additional resources:

Australian Genomics – What is genomic testing? (Infographic)

Centre for Genetics Education – Fact Sheet 15 | Genetic and genomic testing

Centre for Genetics Education – Talking to your family about a genetic diagnosis or test result

Genes in Life – Whole Genome Sequencing

Melbourne Genomics Health Alliance – How could genomics help me?

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