Understanding Genetic Testing Results

A positive result means the lab found a variant in a gene that is believed to cause or increase the risk of FTD.

People with a positive result are told which gene they have a variant in, and any relevant information that may be known about the gene and their specific variant. For example, a change in a specific gene may be more commonly associated with particular symptoms, older or younger average age of onset, or differences in the likelihood of developing symptoms.

The genetic counselor should discuss available research studies or medical recommendations relevant to people with variants in a specific gene.

A positive result is important for other family members. The genes currently associated with FTD are inherited in an autosomal dominant fashion. This means males and females have an equal chance to be affected, and each child of a person with genetic FTD has a 50% chance of inheriting it. The genetic counselor can provide tools and support for communicating genetic results to other family members.

AFTD has a support group for persons at genetic risk of FTD, where members can share their experiences living with and managing their feelings around their genetic risk

A negative result means that the laboratory did not find a variant in the genes tested. 

A negative result in people with symptoms of FTD:

1. The majority of people with an FTD diagnosis but no family history of FTD do not have an identifiable genetic variant.
2. Not everyone with a family history has an identifiable genetic variant.
3. The lab only reports on the genes included in the test order. If the test did not include all genes associated with FTD, additional testing may be needed.
4. Genetic testing today is limited to the genes related to FTD that have been discovered.

Over time, scientists will likely identify additional genes that cause FTD. People with FTD who test negative should consider DNA banking to allow for additional genetic testing in the future, when new genes are identified or there are advances in our understanding of the genetics of FTD.

A negative result in people without symptoms of FTD:

True Negative

If the genetic variant in the family is known, a negative result is a true negative. The lab specifically looked for the familial variant but did not find it. Therefore, the person tested did not inherit the variant; their risk of developing FTD is the same as the general population.

The children of someone with a true negative result are not at risk of inheriting the familial variant and do not need genetic testing for FTD.

Uninformative Negative

If the genetic variant in the family is unknown, a negative genetic test result in a person without symptoms is considered an uninformative negative.

It is possible their relative's FTD could be caused by a gene that has yet to be identified. To help avoid an uninformative negative, a symptomatic person should be the first person tested in a family, whenever possible.

When testing finds a genetic variant whose impact is uncertain, the result is a variant of uncertain significance (VUS). Labs may offer free testing to family members of a person with a VUS if they believe further tests could help clarify its impact.

If additional family testing does not clarify the impact of the variant, people with a VUS should check in periodically with their genetic counselor to see if any new information has become available to clarify their result.

Retesting in the future may be needed following a VUS result, when more FTD-associated genes are identified. You may want to consider DNA banking, which preserves a DNA sample for testing at some point in the future.

Our current understanding of genetic variants draws predominantly from people of European, and primarily Caucasian, backgrounds. As a result, people of color – including but not limited to African, Black, Asian American/Pacific Islander, and Hispanic individuals – are more likely to receive VUS results. Additional work to diversify genetic research and increase the availability of clinical genetic testing in diverse populations is needed to reduce this disparity.