Family variant testing: what to do when a relative has a confirmed genetic finding
Recent Posts
Related Posts
When a relative has a confirmed genetic finding, the usual next step is family variant testing, a targeted test that checks whether another family member carries the same variant. Offering it to relatives one step at a time is known as cascade testing. Whether the finding came from reproductive carrier screening, a diagnostic test or a proactive screen, blood relatives may share it, and knowing early can help them plan a family or start prevention. A genetic counsellor can work out who in the family is most likely to benefit, help with the conversation and arrange testing, which usually needs only a cheek swab.1,2
Key takeaways
- Family variant testing looks only for the specific variants already found in a relative, and Genotype Health’s test can check up to ten variants at once.
- Cascade testing offers this test to relatives step by step, starting with parents, brothers, sisters and children.
- Fewer than half of eligible relatives are currently tested, often because the news never reaches them.
- A genetic counsellor assesses the family, recommends who should be tested and helps with sharing the result.
- Family variant testing does not replace carrier screening for a reproductive partner, who needs their own full screen.
What are cascade testing and family variant testing?
Every person inherits half of their genes from each parent, so a variant found in one person is often present in close relatives too. Cascade testing is the process of letting those relatives know and offering them testing, beginning with the people most likely to share the variant (parents, brothers, sisters and children) and moving outwards to aunts, uncles and cousins as each new carrier is found.1
Family variant testing is the test used at each step. Because the exact variant is already known from the first person’s laboratory report, the laboratory only needs to look for that change rather than analysing whole genes. Genotype Health’s Family Variant Testing can look for up to ten known variants in a single test, which helps when a family has more than one finding, or when a recessive condition in the family involves two different variants. This makes the result clear and focused: a relative either carries the family variant or does not. It is different from reproductive carrier screening, which looks across many genes in someone with no known variant to find out whether they carry anything that could affect their children.
Why does a relative’s genetic finding matter for the rest of the family?
The value of a family result depends on the condition. For variants linked to Lynch syndrome, familial hypercholesterolaemia or inherited breast and ovarian cancer, relatives who carry the variant can start earlier checks or preventive treatment, while those who do not can often avoid extra screening. Finding people before symptoms appear gives prevention and early treatment the best chance of working.1
For carrier findings, the benefit is reproductive. When reproductive carrier screening shows that someone carries a variant, their brothers and sisters are much more likely than the general population to carry the same one.3 A sibling who learns this before starting a family can have their partner screened and, if both are carriers, consider options such as preimplantation genetic testing during IVF or testing in pregnancy.
Despite these benefits, cascade testing often stalls. A recent review of 30 studies found that only about one in three relatives at risk of hereditary breast and ovarian cancer went on to be tested, and uptake was lower among more distant relatives.4 One of the main reasons is simple. The information has to travel from person to person, and in many families it never reaches everyone who needs it.2
How does a genetic counsellor work out who should be tested?
A genetic counsellor starts by reviewing the original laboratory report and drawing a family tree that covers at least three generations. The inheritance pattern of the variant then shapes the plan. For a dominant condition, each child, brother or sister of someone with the variant has a 50% likelihood of sharing it. For a recessive carrier finding, brothers and sisters are the first priority, because they are most likely to be carriers too. For an X-linked variant, the counsellor looks closely at the mother’s side of the family and at female relatives who could pass it on, or in rare cases a father who could have passed a milder variant on to all his daughters.
From there, the counsellor recommends which family members should be offered testing and in what order, usually starting with first-degree relatives and widening the circle as results come in. Age matters as well. For conditions that begin in adulthood, Australian guidance recommends waiting until a young person can make their own decision, unless testing earlier would change their care.5 The counsellor will also explain that a reproductive partner of a carrier cannot use family variant testing, since any variant they carry may sit elsewhere in the gene, so they need a full carrier screen of their own.
How can someone tell their family about a genetic finding?
Sharing a genetic result can feel daunting, particularly when family members live far apart, are not close or have never discussed health. Some relatives will want to know straight away, others need time, and some may choose not to be tested, which is their right (although they might find out anyway if their descendants decide to be tested). Research suggests that support with family communication improves understanding, although no single approach works for every family.6
A genetic counsellor can help by talking through who to tell first, how to explain the result in plain language and how to answer common questions. Many people find it easier to share a written summary rather than explain the details themselves. In Australia, privacy guidance updated in 2025 also confirms that, with a patient’s consent, health professionals may contact at-risk relatives directly in some circumstances.2
“Most people want to protect their family but are not sure how to start the conversation. Our role is to make that easier, with clear information they can pass on and support for whatever questions come back.”
Dr Mona Selah, Head Genetic Counsellor, Genotype Health
How does family variant testing work with Genotype Health?
Every Genotype Health test starts with a detailed medical and family history form, completed when the test is purchased. It is thorough for a reason. Having this information from the outset means Genotype Health’s genetic counsellors can quickly assess risk across the family and, if a significant finding is made, arrange Family Variant Testing referrals for relatives without delay. Someone whose relative received a finding elsewhere can also book an appointment, and the counsellor will review the confirmed result alongside their history. Because the test is built around specific known variants, the variants must appear in a written laboratory report, so a copy is needed. The counsellor then identifies which relatives would benefit from testing and explains what a result could mean for each of them.
Where there are significant findings, the counsellor creates a unique digital referral link for each family member recommended for testing and sends these links to the person with the original result. This means they can speak with their relatives in their own way and their own time, and pass on the right link to each person. A relative who decides to go ahead uses their link to start the process, receives counselling before and after testing, and provides a sample using a simple cheek swab, also known as a buccal swab, collected at home. Their result is reported specifically for the family variant.
For relatives who are planning a family, a result for one variant is only part of the picture. Reproductive carrier screening looks across many genes at once and is still recommended for both partners, because each could carry variants that are unrelated to the family finding. Genotype Health offers Core Carrier Screen, a bulk-billed test for eligible Australians that checks three conditions (spinal muscular atrophy, cystic fibrosis and fragile X syndrome), and Lineova, a more comprehensive screen of 461 genes with ancestry panel options. A genetic counsellor can help relatives decide which approach, if any, suits them.
What does a family variant test result mean?
Because the test looks only for known variants, the answer is usually straightforward. If a relative does not carry the family variant, they have not inherited the family’s increased chance for that condition, and for a carrier finding, their own children cannot inherit the variant from them. If they do carry it, the genetic counsellor explains what this means for their health or family planning and which next steps are recommended, which may include specialist referral, earlier checks or partner screening. Their result also extends the family map, as their own children, brothers and sisters may then be offered testing in turn.
Is family variant testing available through public services?
Public funding is sometimes available to relatives, for example through Medicare items for relatives of people with certain hereditary cancer or inherited heart condition variants, or through a public genetics service, listed in the directory of genetic services across Australia.7 Genotype Health’s tests are analysed overseas and are not eligible for Medicare rebates, so checking public options first can be worthwhile. See Medicare funding for genetic testing in Australia.
Has a relative had a genetic finding?
Thinking about starting a family? See how Genotype Health’s carrier screening tests can help: Lineova carrier screen or Core Carrier Screen.
Want help working out who in the family should be tested? Book a genetic counselling appointment.
More questions about family variant testing
Can a relative have family variant testing without the original laboratory report?
Usually not. The laboratory needs to know the exact variant. If the report is not available, a genetic counsellor can advise on other options, such as broader testing.
If a relative does not carry the family variant, are they free of any risk?
They do not carry that variant, so their chance for that condition returns to about the population level. Other inherited and non-inherited factors still apply.
What if a family member does not want to know?
Choosing not to be tested is a valid decision. Sharing the information still lets them decide for themselves, now or later. Information they or other relatives share with their adult descendants might eventually and indirectly indicate their risk, or might in some cases reveal family information that parents decided not to disclose.
Can life insurers in Australia use a family variant test result?
Since 8 October 2026, Australian life insurance companies have been prohibited from using an unfavourable genetic result to refuse a policy or reduce cover, although health conditions that have already been diagnosed can still be taken into account. Read more in genetic testing and your insurance.
How accurate is family variant testing?
Family variant testing is highly accurate, but there remains a small risk of laboratory or clerical errors, or of errors due to unknown family relationships.
Related reading
- Everything you need to know about genetic testing and counselling
- Whole exome vs whole genome sequencing: what’s the difference?
- Understanding your genetic test report: a guide to common terms
- What is genetic counselling? A plain-language guide
References
- Centers for Disease Control and Prevention. About cascade testing [Internet]. Atlanta (GA): CDC; [updated 2026 Aug 12; cited 2026 Oct 8]. Available from: https://www.cdc.gov/cascade-testing/about/index.html
- Tiller J, Otlowski MFA. Clinicians’ discretion to contact patients’ at-risk relatives about their genetic risk: new guidance from Australia’s privacy regulator provides timely clarification. Med J Aust. 2025;223(3). doi:10.5694/mja2.52712
- Cystic Fibrosis Trust. Testing for cystic fibrosis carriers in families [Internet]. London: Cystic Fibrosis Trust; 2024 Oct [amended 2025 Jul; cited 2026 Oct 8]. Available from: https://www.cysticfibrosis.org.uk/sites/default/files/2025-10/Cascade_Screening_Sep2025.pdf
- Uptake of cascade genetic testing for hereditary breast and ovarian cancer: a systematic review and meta-analysis. Clin Obstet Gynecol. 2024 Oct 18. doi:10.1097/GRF.0000000000000895
- Vears DF, Ayres S, Boyle J, Mansour J, Newson AJ. Human Genetics Society of Australasia position statement: predictive and presymptomatic genetic testing in adults and children. Twin Res Hum Genet. 2020;23(3):184–9. doi:10.1017/thg.2020.51
- Baroutsou V, Underhill-Blazey ML, Appenzeller-Herzog C, Katapodi MC. Interventions facilitating family communication of genetic testing results and cascade screening in hereditary breast/ovarian cancer or Lynch syndrome: a systematic review and meta-analysis. Cancers (Basel). 2021;13(4):925. doi:10.3390/cancers13040925
- Centre for Genetics Education. Genetic services [Internet]. Sydney: NSW Health; [cited 2026 Oct 8]. Available from: https://www.genetics.edu.au/SitePages/Genetic-Services.aspx
