Genetic testing – should you consider it?

Chances are genetic testing has been mentioned by a doctor, a support group or a random on Facebook. So, what are the benefits? Genetic counsellor Rachel Pope-Couston explains.  

WHAT: What does genetic (or genomic) testing look for?  

Genetic testing is trying to find genetic changes in a person that explain their condition or symptoms. Some genetic or genomic tests will be looking for a single letter in a gene, which stops the gene from working properly, while others will be looking for missing or extra chromosome information, like a duplication or deletion.  

What are some of the results you can receive?  

Generally, there are three types of results: diagnostic, uninformative, and uncertain. When a pathogenic variant is found, then the test is diagnostic. This means that the genetic explanation for the condition has been found. Uninformative results are where no genetic variants have been found that could explain the condition or symptoms. Uncertain is where a genetic variant has been found, but it is not yet clear whether it is the explanation for the condition. 

WHEN: When would genetic testing be offered to someone with a suspected genetic condition? 

This will depend on a range of different things. For example, some people are born with symptoms that suggest a genetic condition could be the explanation for their experience, while other people won’t develop symptoms until adulthood. For some people, a genetic test will be performed routinely by a specialist involved in their care, and then they will be referred to a genetic specialist. For others, they may be referred straight to a genetics service, to help decide what type of genetic testing will be most helpful. 

Getting access to a genetic test, genetic service, or any other relevant speciality can take a long time. The term ‘diagnostic odyssey’ is often used to refer to the experience of searching for a diagnosis for unexplained symptoms. Unfortunately, there are many people and families that still experience a very long, drawn out journey to reach a diagnosis, even once they access a genetic service. Some people will undergo all available tests, including genetic/genomic testing, and still not have a certain diagnosis. 

WHY: Why might you want to do the testing? 

A genetic test may be able to provide a diagnosis for what is going on. Having a name for the condition (or identifying genes responsible for a very rare condition) makes it easier to find information and learn more about what the future may hold. As a parent, the information may be helpful in planning further children, or if the diagnosis is yours, it can help you plan for a family in the future. A diagnosis or even a ‘non-diagnosis’ also facilitates a connection with other families and individuals who may have shared a similar journey. 

Why might you not want to do the testing?  

Sometimes, knowing more about what the future may hold can be scary, especially if the condition is likely to get worse. Sometimes a genetic test will not add any information that’s needed right then (for example, if someone already has a clinical diagnosis). Some people may want to investigate the implications for things like life insurance before they get testing. A genetic counsellor can also help you consider these issues. You do not have to decide to have testing to speak to a genetic counsellor. 

Why isn’t a genetic diagnosis always possible?  

The genetics community has made huge progress in what we know about human genetics, but we don’t know everything at present. Sometimes, the technology doesn’t work well enough yet to find a genetic cause that is there. Or, sometimes our understanding may not be good enough to interpret every genetic change (like variants of uncertain clinical significance mentioned above). Sometimes, the genetic cause may not be a single genetic change, but a lot of small contributing factors. 

HOW: How is the sample collected?  

Most genetic and genomic testing is done by collecting a small amount of blood. However, many tests can now be done using a buccal swab which collects the skin cells from the inside of the cheeks, or by collecting a sample of saliva in a ‘spit tube’. 

How is the testing done?  

In Australia, clinical genetic testing is performed in a NATA-accredited laboratory which is experienced in providing the testing. Some tests look at a single gene, some, many genes at once (a panel), others look at thousands of genes (exomes), or every gene in the body (genome). 

How will I get the results?  

These should be provided to you by a professional who understands the results, like a paediatrician or a genetic health professional. Before testing is done, you should be involved in planning when and how you will receive the results. 

WHO: Who will be offered genetic testing?

In the public system there are clear guidelines on who will be offered a genetic test. Genetic testing usually starts with the person who has the most symptoms. If the person is a child, sometimes one or both parents will also be asked to undergo testing at the same time, or after the result for the first person is available. If a clear genetic diagnosis is made, sometimes others in the wider family will then be able to access genetic testing.  

It can be frustrating not to know which tests should be done and when, who should have them, and why they might be helpful. It’s important to understand, there is no clear answer to many of these questions and each family’s journey with genetic testing will be different. You can seek a referral to your local genetics service and speak to a genetic health professional. Genetic counsellors are skilled in helping people work through complex information to make decisions that are right for them and their family. They can also provide support in understanding genetic test results and genetic conditions once they are diagnosed. 

There are a growing number of ways to access genetic testing outside of a public clinic, and in the next edition of Source Kids magazine, we’ll talk more about the different options and their pros and cons.  

Rachel Pope-Couston, MGC, FHGSA is a registered and certified genetic counsellor and is the current president of The Genetic Support Network of Victoria (The GSNV) Committee of Management.