A pathogenic variant identified in one person can create an opportunity for relatives to understand their own inherited risk. Cascade genetic testing extends testing through a biological family after a relevant variant has been identified. In hereditary cancer care, this can identify relatives who may benefit from prevention or earlier detection before cancer develops. Its clinical value depends on connecting the result to appropriate counselling and care. NCI’s professional overview describes this approach.
Start with the documented finding
Obtain the original laboratory report where possible. A family recollection of a positive genetic test may leave the gene, exact variant and interpretation unclear. CDC specifically recommends sharing genetic reports to help relatives access appropriate testing. A useful referral therefore includes the report alongside the relationship to the person tested and the relevant family history. CDC’s cascade testing guidance explains what families can share.
For hereditary cancer, establish whether the finding came from inherited-risk testing or tumour analysis. Tumour sequencing can sometimes reveal an inherited change, but it does not replace germline testing. When a familial variant is documented, testing may target that specific change; broader testing may be appropriate when the relative’s own history raises additional questions. NCI’s genetic testing fact sheet distinguishes these testing contexts.
Choose relatives and timing deliberately
The family relationship and inheritance pattern guide whom to approach first. Parents, siblings and children are often the starting point. Results can then help identify which branch of the family needs further assessment. If a close relative is unavailable or declines testing, more distant relatives can still be considered. Genetic testing for conditions that begin in adulthood is generally deferred in children. CDC describes these practical considerations.
Counselling should distinguish the chance of inheriting the variant from the chance of developing disease. For an autosomal dominant cancer predisposition, a child of a heterozygous carrier has a 50% chance of inheriting the variant. That probability does not mean a 50% chance of cancer: disease risk depends on the gene and its penetrance. NCI’s professional summary discusses inheritance and risk interpretation.
Explain what each result answers
The familial variant is present
A positive result establishes that the tested relative carries the familial variant. Its implications depend on the condition. Genetic results may establish a diagnosis, identify carrier status or indicate susceptibility to a future disorder. A positive predictive result often cannot determine whether symptoms will develop, when they will begin or how severe they will be. MedlinePlus explains these limits.
The familial variant is absent
In hereditary cancer testing, absence of a documented familial pathogenic variant can constitute a true negative. This differs from an uninformative negative when no causal familial variant has been established. A true negative does not eliminate ordinary cancer risk. Follow-up still requires consideration of the person’s clinical history, family history and other risk factors. NCI explains negative-result interpretation.
Document the scope in plain language: the known familial variant was not detected. Avoid expanding that statement into a claim that all genetic disease has been excluded. A negative result may reflect the limits of what was examined, and further testing can sometimes be needed when clinical findings remain unexplained. MedlinePlus’s results guide provides the broader context.
Keep uncertainty separate from predictive care
A variant of uncertain significance has insufficient evidence for a clear interpretation. It should not be presented as an established familial cause. In cancer genetics, such findings generally do not determine medical management. Research may eventually clarify a variant, but an unresolved finding does not provide the same clinical basis for predictive testing as an established pathogenic variant. NCI describes VUS interpretation.
Support communication and follow-through
Offer a family letter and a route to genetic counselling. Respect a relative’s decision to defer or decline testing; receiving information does not oblige someone to act immediately. CDC offers communication options. For relatives who proceed, arrange post-test discussion and condition-specific risk assessment. Cascade testing becomes useful care when the result is understood and connected to an appropriate management plan. NCI describes post-test counselling.