Guidelines for genetic testing referral
(Inside Aotea, September 2011)
By Alison McEwen, genetic associate, Central Regional Genetic Services, Wellington Hospital
Genetic testing is available for an increasing range of conditions. It is also currently fashionable with the media and, as a result, patients often request particular tests, sometimes based on incorrect information they have seen.
This article addresses some of the issues to consider when arranging genetic testing, and includes guidelines for referral to genetic services.
Why get genetic testing?
- A genetic test may be used to make or confirm a particular diagnosis; for example, diagnostic testing for Huntington disease may be indicated in a person with choreaform movements and other symptoms suggestive of Huntington disease.
- Predictive or presymptomatic testing may be available to people with a known family history of specific inherited conditions, for example, Huntington disease, myotonic dystrophy and familial cancers where the specific mutation has been identified in an affected family member. These tests are only available after consultation with a genetic associate or clinical geneticist.
- Prenatal diagnosis or preimplantation genetic diagnosis may be available to individuals with known genetic conditions and a previously identified mutation, again in consultation with Genetic Services staff.
- Carrier testing may be used for reproductive planning for individuals with a family history of some common recessive conditions, for example, carrier testing for cystic fibrosis in the parents of an affected child and in the parent's siblings.
Is consultation required?
The majority of families requesting these genetic tests should be referred to Genetic Services for consultation.
Laboratories will often not accept blood samples unless an individual has had a consultation with a genetic service.
Are there any issues with genetic testing?
- Genetic testing is expensive. Tests often cost more than $1,000. Genetic Services covers the cost of testing in patients we have seen. Tests requested by other health providers will be charged back to them.
- Written, informed consent is required for all genetic tests. Informed consent includes discussion about the potential psychological impact of a result for the individual and their family, the potential for insurance discrimination and the storage of results and DNA samples. Some overseas laboratories require specific consent forms and detailed clinical information.
- Genetic test results often have implications for the family of person being tested. It is crucial this is discussed in advance of testing.
The results of genetic tests may be complex and require interpretation. For example, a variant of uncertain significance may be reported. It is important this is correctly interpreted so appropriate surveillance and advice can be offered to family members.
There are a number of common, funded genetic tests that medical staff outside Genetic Services can request.
These include genetic testing of adults for haemochromatosis, factor V Leiden and the other thrombophilias, and carrier testing for cystic fibrosis.
It is usually not appropriate to test children for these disorders without appropriate counselling, so consultation with Genetic Services may be advised if a family is seeking to test their children.
What assessment does Genetic Services make of a genetic test request?
When requesting a genetic test, the following questions may be considered:
- Is it possible to interpret the result — for example, APOE test results?
- What is the utility of the test — for example, haemochromatosis testing in children?
- Do we know what mutation to test for — for example, cystic fibrosis carrier testing?
- Are we testing the right person? In many instances genetic testing will not be possible without first testing an affected relative.
- What follow up or treatment can be offered?
Who to contact for further information
If you have any questions about genetic testing or would like to refer a patient to Genetic Services, please contact us:
Central and Southern Regional Genetic Service (areas south of and including Hawkes Bay and Taranaki):
Toll-free -- 0508-364-436
Northern Regional Genetic Service:
Toll-free -- 0800-476-123
Email: genetic.services@ccdhb.org.nz
