Genetic and genomic testing
In Australia genetic and genomic testing can only be ordered by a medical professional. There are many different types of genetic and genomic tests and it is important that the type of test you have is appropriate for your situation. The way in which these tests are ordered and funded varies.
In South Australia clinical genetics and genetic counselling services are provided through selected specialists and the SA Clinical Genetics Service. A referral from a medical practitioner is required to access these services.
When are genetic and genomics tests used?
Diagnostic testing is used to identify or confirm a clinical diagnosis. Diagnostic testing looks to see if a patient carries the same genetic changes that have been previously reported to cause the same condition in other patients. This testing can be performed at any time and the results may influence a individual's healthcare plan. Not all disorders can be diagnosed using genomics.
Genes come in pairs, with one copy inherited from your mother and the other copy inherited from your father. For 'recessive' diseases both copies need to be damaged before an individual will become sick. If both partners carry a damaged gene their child has a 25% of being affected. Carrier testing can be used to determine whether a parent 'carries' a damaged gene. Carrier testing is only used in cases where one or both of the parents are suspected to be at high-risk of carrying the damaged gene.
Prenatal testing is used to detect changes in a fetus's genes or chromosomes before birth. This type of testing is offered during pregnancy if there is an increased risk that the baby will have a genetic or chromosomal disorder. In some cases, prenatal testing can lessen a couple's uncertainty or help them make decisions about a pregnancy. It cannot identify all possible inherited disorders and birth defects, however.
Pharmacogenomics testing is used to predict how patients will respond to drug therapy based on their individual genetic makeup. Differences between individuals can affect drug absorption, metabolism, or activity. Therefore, while one treatment regimen may work well for one individual, the same regimen may cause adverse effects for other individuals.
Predictive testing is used to detect gene mutations associated with disorders that appear after birth, often later in life. These tests can be helpful to people who have a family member with a genetic disorder, but who have no features of the disorder themselves at the time of testing. Predictive testing can identify mutations that increase a person's risk of developing disorders with a genetic basis, such as certain types of cancer.
Genomic testing can also be conducted in a research environment. The purpose of research testing is to push the boundaries of discovery. Research tests are not validated for diagnostic use and the results of these tests may not always be provided to patients. Research testing helps to develop new test methods, identify novel disease gene and to advance our knowledge of disease mechanisms.
What are genetic or genomic tests looking for?
There are many different types of genetic and genomic tests. These tests can look for:
- changes in the DNA sequence and/or,
- changes in the order, arrangement or structure of the genome.
Most tests only look at the part of the genome that is relevant to the clinical situation. This means that in some cases the whole genome may be sequenced, whereas in other cases analysis will be restricted to the exome or even just a single gene. Read more about the different techniques used on the genomics technology page.
Before you start testing
There are some things you should think about before you start testing.
You should be provided with information about the test and have the opportunity to discuss this with your doctor or a genetic counsellor. This is because these tests can provide important information about your health and may also have implications for your family, insurance and employment.
What happens when I get tested?
A genetic test usually involves collecting a sample of blood. Genetic material (DNA) is then extracted from the blood sample for analysis. Sometimes DNA can be extracted from hair or saliva samples instead of blood, or if you are a cancer patient the DNA may be taken from your tumour.
If you have a genetic test, the results will be sent to you and your referring doctor. It may take several months for the results to become available. If the laboratory identifies a genetic error in your DNA sample they will arrange another appointment. At this appointment a clinical geneticist and/or a genetic counsellor will talk to you about your result and discuss what the result means for other members of your family.
It is also important to recognise that genomic testing is still a young technology and it can be challenging for scientists to interpret genetic information. This means that genomic testing can produce uncertain results. We are currently building national and international databases to help scientists and clinicians link genomic results to clinical outcomes. As these databases expand we will be much better at interpreting genomic data, but for some patients this means that genomic testing may not yet be able to provide an answer.
Why have I been referred for genetic counselling?
Genetic counselling is about helping people understand and cope with the effects of genetic disorders on their lives and the lives of their families.
There are a number of possible reasons for your doctor making this referral including:
- you have a genetic condition in the family, and want to know the chance that you and/or your children might develop the condition
- you have a genetic condition and want specialist advice about the genetic aspects of the condition
- you have health issues which may be due to a genetic condition, and want to see if a diagnosis can be made
- you have a strong family history of cancer, and want to know if you are at increased risk of developing cancer. If you are known to be at increased risk of cancer, to discuss the options that are available to manage this risk.
- whether you and/or your partner are carriers of a genetic condition or chromosome abnormality
- to understand what caused a birth defect, biochemical disorder, or chromosome problem in your baby, and the chance of a similar problem in another pregnancy
- to understand whether you and your partner are at risk of having a baby with a birth defect because:
- you are related
- you are concerned about the effects of medications, drugs or chemical exposure in pregnancy
- to consider genetic testing.
I want to order my own test
At the moment it is not possible to order your own test in Australia, however, if you think testing is relevant or useful, you can discuss this with your doctor and they may be able to order testing for you or refer you to a specialist for further investigation. Funding for this testing is very limited and tests are only provided where medically relevant. For those who suffer from, or might have inherited a serious condition, it may be possible to participate in one of the many research studies conducted in Australia.
Alternatively, if you are interested in sequencing your genome to understand your personal health profile, Sydney company Genome.One, currently offer this service as part of a comprehensive private medical assessment.
If these are not options for you, it is possible to order testing (usually online) from overseas providers (also called direct to consumer (DTC) testing). The majority of these tests are designed to provide you with non-health information, for example you can order tests that tell you about your ancestry or tests that design personalised items of clothing based on your DNA sequence. It is likely, however, there will be more health-related testing available in the near future.
It is recommended that you talk to your healthcare provider before ordering a health-related test as there can be repercussions for you and your family. Currently the quality of these tests is unknown, and it is difficult as a consumer to evaluate whether the results are accurate or reliable. It is possible that these tests are not able to detect what they are claiming or that they find 'problems' that don't actually exist causing you undue worry.
Points to consider before ordering a test:
- Is the test appropriate for my needs and will it meet my expectations?
- Is there any assurance that test will be accurate and reliable? Most countries have regulatory systems that govern diagnostic testing. It recommend that you only order health tests through a provider that is accredited and accountable in their country.
- Is the test validated? Even accredited providers can offer non-validated tests. Ask whether both the laboratory and the test are approved.
- What type of test are they actually offering? Not all genomic tests are equal and there are many different technologies used in genomic testing. Make sure you understand the limitations of the technology the company is providing.
- Where is my data stored and who is it shared with? Even if you are ordering a non-health test for just for fun, your genomic data is a valuable commodity and some companies on-sell your genomic data to other companies.
- Is the test scientifically valid? Not all online tests are based on scientific rigor, be particularly wary of tests associated with sales of a particular product based on the test outcome e.g. dietary supplements.
- Do I understand the potential implication of the results for me and my family?