Genetic testing

Genetic testing typically involves:

  • A Genetic counselling appointment. See Genetic appointments for more information. 
  • Collection of specimen (urine/blood/saliva)
  • An appointment to obtain the results of testing.

Before deciding if you would like to proceed with genetic testing, it may be helpful to consider some of the reasons for and against it.

Speaking to a geneticist or genetic counsellor will help you decide whether genetic testing is the right decision for you and your family right now.

Reasons people wish to have genetic testing
  • To confirm/find a diagnosis
  • Guide for future family planning and pregnancies
  • Explanation of family history
  • Assess if there are health or reproductive implications for the wider family (conditions may have implications for not only an individual but also for others in the family, including siblings, parents, aunts, and uncles)
  • Helping to come to terms with why the child has epilepsy
  • Access to financial and social supports
  • To assess if a diagnosis helps their doctor better treat or manage the child’s epilepsy.
Reasons people wish not to proceed with genetic testing
  • A diagnosis of the genetic condition may reveal a more severe disease than initially predicted
  • The family are not planning further children
  • Concern about revealing non-maternity or non-paternity
  • Concerns about discrimination (e.g. life/mortgage /income protection insurance applications, NOT health insurance).
  • Concerns about privacy. 

Types of tests

Chromosome microarray

Epilepsy gene panel

  • This test examines the DNA sequence of multiple/a targeted set of genes that are associated with epilepsy at one time
  • Results for this test are usually available within 3-4 months
  • Learn more about genetic and genomic testing.

 

Whole exome testing and whole genome testing

  • The DNA sequence within a gene is made up of exons (protein-making) parts and introns (non-protein-making) parts. Most genetic conditions occur as a result of changes within the DNA sequence of the exons.
  • Whole exome sequencing examines the DNA sequence of all the exons of all our 20 000 genes at the same time  
  • Whole Genome Sequencing examines the DNA sequence of the introns AND exons of all our 20 000 genes at the same time
  • Results for exome sequencing are usually available within 4-6 months
  • Genome sequencing is not routinely available in Australia        
  • Learn more about genetic and genomic testing.

Testing outcomes

Outcomes of genetic testing

  • Outcomes of testing will depend on the type of testing undertaken.
  • All possible outcomes of testing should be discussed with your ordering clinician prior to undertaking testing as part of an informed consent process.

Possible results may include (but are not limited to):

Pathogenic or likely pathogenic

A definitive explanation for the epilepsy. The change in the gene will affect an individual and cause epilepsy.

Variant of uncertain significance

The effect of the change on the gene is unclear.

Additional information and evidence may be required in order to work out if this change will cause epilepsy or is a normal variation.

Incidental and additional finding

A change in a gene which causes a health issue which is unrelated to the reason for the test.

Example: finding a change in a gene associated with heart disease, when the reason for testing was epilepsy.

Negative

There are multiple reasons for a negative result, these include:

  1. The cause of the epilepsy is not genetic
  2. The gene causing the epilepsy has not been discovered yet
  3. The test was not advanced enough to detect the gene change that causes epilepsy.

Testing limitations

Remaining uncertainty with testing:

Information limitations with a diagnosis

  • Genetic epilepsies are often rare. Lack of long-term studies on large numbers of patients with the same underlying genetic condition mean that clinicians are often unable to provide accurate prognostic (seeing into the future) information.
  • As new genes are discovered, the first cohort described often have similar (and often more severe) medical complications.
  • Over time, with more individuals being tested, a clearer picture of the full spectrum of the condition will be seen, but this can take several years.

What does it mean if genetic testing is negative?

  • A negative result (no cause found) one day does not rule out the possibility of a genetic condition in an individual in the future.
  • Information about genetic causes of health conditions changes over time.
  • This is because there remains the possibility that new gene discovery, technology or understanding will clarify the reason when future reanalysis or more testing is available in the future.

Reanalysis

An individual who receives a negative result on an exome or genome will generally be advised to consider reanalysis (the laboratory reassessing the data for a diagnosis) as future discoveries may provide a diagnosis. 

The current suggested reanalysis timeframe is every 18 months.

Testing costs

Payment and cost

Medicare rebatable testing is available for certain situations when testing in genetic epilepsy. Out-of-pocket fees will often be covered by the hospital or health service if the patient is being seen through the public health service, although this will vary between services and states.

Costs are subject to change (usually becoming cheaper) and are laboratory dependent. We advise that individuals seek advice from their medical practitioner or local genetics service about current costs if the preference is to pay for a test privately.

Medicare covers the following tests with requirements. If Medicare does not cover the individual patient case, options for fee coverage should be discussed with the ordering clinician:

  • Chromosomal Microarray (also known as Array, CGH, SNP array): Medicare rebate (with referral requirements to be met)
  • Fragile X PCR: Medicare rebate (with referral requirements to be met)
  • Urine Metabolic Screen: Medicare rebate in some states/territories (with referral requirements to be met)
  • Gene Panel / Exome / Whole Genome Sequencing: Medicare rebate