When Is Genetic Testing For Dementia Appropriate
In some cases, it may seem likely that a persons dementia is caused by a single-gene change for example, if the person has a very strong family history of dementia. In these cases, it may be appropriate to offer genetic testing to the person and to their family.
However in most families dementia will not be caused by a single-gene change. In these cases, genetic testing will not be appropriate. This is because testing for risk variants does not provide any certainty about the persons chances of developing dementia.
Genetic Research For Alzheimers Disease
Researchers think there are probably many more genes that affect the risk of Alzheimerâs. Discovery of these genes will help doctors:
- Understand the disease better and learn why it affects certain people in certain ways
- Learn more about what increases your risk of getting it
- Identify people who are at higher risk so they can home in on preventive care
- Develop new treatments
Predictive Testing And Genetic Counselling
Predictive testing can be stressful. If a person receives a positive test result, they will know for certain that they will develop dementia. This can be very difficult information to take in.
For this reason, predictive genetic testing will only be done with genetic counselling both before and after the test. This is to make sure that the person is aware of what it means to have the result of a genetic test, both for them and for their family. Many people have counselling but dont then go on to take a test.
Also Check: Is Dementia Considered A Terminal Disease
What You Need To Knowfirst
NEW YORK Persons wishing to learn their genetic risk for Alzheimers disease by way of an at-home genetic testshould first consider consulting with their doctor and a genetic counselor, according to a commentary authored by AFAs Medical, Scientific & Memory Screening Advisory Board, among other recommendations aimed at physician-scientists, policymakers, and the commercial genetic testing industry. The article was published online today in the Journal of Alzheimers Disease .
Before pursuing any kind of genetic testing, it is essential that consumers are fully informed and understand the benefits, limitations and other implications of learning ones personal health information, says Charles J. Fuschillo, Jr., President and CEO of the Alzheimers Foundation of America . This includes having insight on how a test result might impact the individual and their family emotionally, particularly in the case of Alzheimers in the absence of a cure, or an effective treatment.
The number of consumers accessing their genetic information has exploded, since the April 2017 FDA approval of direct-to-consumer testing for genetic disease risks. Among the genetic tests available is one to determine APOE statusapolipoprotein-E, a susceptibility gene for late-onset Alzheimers disease. And with effective and sustained marketing campaigns by commercial testing entities, the sales of the tests have already skyrocketed .
Technical Notes
Red Flags To Consider Genetic Testing Or Genetic Consultation
Genetic testing for AD is only available for a small number of families with early-onset familial AD, with testing likely to be initiated in a living affected relative. If a gene mutation is found, other family members are eligible for testing for the identified family mutation. Clinical testing is currently not available for late-onset familial AD or sporadic cases. When there are multiple related affected individuals, research testing may be available. APOE e4 testing is not recommended for risk assessment because of low sensitivity and specificity.
Consider a genetics consult for patients with:
AD with age of onset < 60-65 years
Late-onset AD and multiple affected close relatives
Close relatives of the above two types of patients
A family member who has an identified mutation in the APP, PSEN1 or PSEN2 genes
to connect to your local genetics centre.
Read Also: How Does Music Help Dementia Patients
My Father Has Been Diagnosed With Probable Late Onset Alzheimer Disease And His Apoe Genotype Test Is Negative For E4 Alleles Should His Doctor Be Doing Other Genetic Testing
No, not at this time. Forty percent of individuals who have late onset Alzheimer disease are negative for APOE e4 alleles.
Currently, there are only three known genes that are associated with AD. Mutations in each of these genes are associated only with a rare and early onset form of AD. Changes to these genes are not associated with typical or late onset AD. If you have a strong family history of AD that includes multiple family members across several generations, you may want to talk to your doctor about genetic counseling for risk assessment.
The Genetics Of Frontotemporal Degeneration
Frontotemporal degeneration is a group of neurodegenerative diseases that typically present with personality and behavioral changes or language difficulty . Although FTD is among the most common presenile dementias, the range of onset is quite wide . New criteria for bvFTD have recently been published and includes disinhibition, apathy, loss empathy, perseverative/compulsive behaviors, hyperorality, and executive dysfunction . The FTD associated PPA syndromes include non-fluent progressive aphasia and semantic dementia . Corticobasal degeneration and progressive supranuclear palsy are closely related diseases. Patients with FTD may also develop ALS and/or parkinsonism .
The understanding of the pathogenesis of FTD has changed dramatically over the last ten years, with the newest FTD gene being uncovered just a few months ago. Unlike AD, FTD is actually a group of diseases each with its unique pathology. Approximately 40% of FTD is a tauopathy, as is AD. However, whereas in AD equal amounts of 3R and 4R tau are abnormally hyperphosphorylated, in FTD the tau ratio is shifted to 3R tau in Picks disease or 4R tau in CBD and PSP. Mutations in the microtubule associated protein tau gene can cause any of the tau pathologies . FTD with tau positive pathology is now referred to as FTLD-tau.
Read Also: Do Dementia Patients Get Headaches
The Whole Genome Sequencing
The process utilises a new and advanced technology that allows us to read a complete set of your DNA at a single time. The genome is your bodys instruction manual – around 99% of the genome is the same in all human beings. There are around 3 million genetic variations in the 1% difference, and this is what makes you who you are. We analyse these variations using a Whole Genome Sequencing test to reveal your unique genetic makeup.
Using our test, we offer a comprehensive report that provides a deep dive into your biological characteristics. Here we give invaluable information about your diet, metabolism, health conditions, food intolerance and allergies, sleeping patterns, body morphology and even your personality.
The Whole Genome Sequencing Report allows you to make proactive and meaningful changes to your life with actionable insights. From creating an exercise plan to choosing the most effective medicines for your body. With genome sequencing, Dante Labs can help you live a life thats healthier, happier and more informed.
Yes There Is A Blood Test For Alzheimers Genes
While those who develop Alzheimers disease are likely to have similar symptoms, the two main types of Alzheimers are categorized as early-onset, or young-onset, Alzheimers and late-onset Alzheimers. Early-onset Alzheimers disease is less common, accounting for less than 10% of those with Alzheimers, and refers to individuals under 65 who develop Alzheimers. Late-onset refers to individuals 65 and older who develop the disease. Accordingly, researchers have found that there are specific genes or genetic mutations associated with each type of Alzheimers disease. Aside from the two main categorizations of Alzheimers, Familial Alzheimers disease is known with certainty to be linked to geneticshowever, it is quite rare, accounting for 1% or less of Alzheimers cases.
Genetic tests for Alzheimers disease are typically completed in the form of a blood test or saliva test. Below we detail common genes or genetic mutations that are tested for relating to late-onset and early-onset Alzheimers disease.
Recommended Reading: Cause Of Dementia In Young Adults
Does The Parent Need To Know If They Have A Single
Some people may think that they have a single-gene change and want to use PGD to make sure that their child does not have it. However, they may want to avoid finding out whether they themselves have the changed gene. It is possible in some centres to use the technology without the parent finding out if they themselves have the change.
Can Genetic Testing Determine Alzheimers Disease Risk
Having a family history of Alzheimers disease might make you concerned about developing it yourself at an older age. In that case, you may want to undergo genetic testing to know about the probability of developing Alzheimers.
Multiple researchers have highlighted the link between an increased Alzheimers risk and a persons genetics. Scientific findings show that individuals with first-degree relatives that have had Alzheimers are at a greater risk of developing the disease. The risk multiplies further if a person has more than one first-degree relative with Alzheimers.
Although scientific advancements, such as genetic testing, can conveniently detect hereditary diseases, the question remains, would it even be helpful to determine an individuals risk of developing Alzheimers via this technique? Before we know the answer to this question, we must know about the genes and genetics of Alzheimers disease.
Don’t Miss: When Your Spouse Has Dementia
Public Willingness To Undergo Presymptomatic Genetic Testing For Alzheimers Disease
Mohammed H. Alanazy
Abstract
Presymptomatic genetic testing for Alzheimers disease is available for at-risk individuals. This study aimed to investigate the public perception of PGT in Saudi Arabia and determine variables that might influence the decision to undergo PGT. A questionnaire link was posted on Twitter by the Saudi Alzheimers Disease Association and was made publicly available on social media networks. A total of 2935 people participated, of which 59.9% were willing to undergo PGT. Of these, 26.8% reported having a family history of AD, and 0.24% had two family members with early onset AD. The reasons cited for willingness to undergo PGT included the following: to adopt a healthier lifestyle, to ensure appropriate family and financial planning, to seek early treatment, and to relieve anxiety. In multiple logistic regression analysis, willingness to undergo PGT was negatively associated with having a self-reported family history of dementia and was positively associated with marital status . In conclusion, PGT for AD seems to be well accepted in this large Saudi cohort. The reasons cited are similar to those reported elsewhere in the literature.
1. Introduction
2. Methods
3. Analysis
4. Results
5. Discussion
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
How Is It Used
APOE genotyping is sometimes used as an added test to help in the diagnosis of probable late onset Alzheimer disease in symptomatic adults. However, the association of the e4 allele with late onset AD does not mean that it causes AD, only that more people with late onset AD have e4 alleles compared to similar aged peers without late onset AD. For this reason, APOE genotyping is referred to as susceptibility or risk factor testing since it indicates whether there is an increased risk of AD but is not specifically diagnostic of AD. For example, if a person has dementia, the presence of APOE e4 may increase the likelihood that the dementia is due to AD but does not prove that it is.
There are no clear-cut tests to diagnose Alzheimer disease during life. Healthcare practitioners can, however, make a reasonably accurate clinical diagnosis of AD by ruling out other potential causes of dementia and checking for a genetic predisposition to AD with APOE genotyping as supplemental information in conjunction with tau protein and beta amyloid testing.
Also Check: How Many People Have Dementia In Us
Who Is At Most Risk
Genetics plays a role, so a person with the 4 variant in the APOE gene has a higher likelihood of developing late-onset Alzheimers, but other non-genetic factors are also associated with higher or lower risk. And many of these factors are interrelated diet, exercise, and heart health, for instance.
How Do Genes Work
Genes are the basic building blocks that direct almost every aspect of how youâre built and how you work. Theyâre the blueprint that tells your body what color your eyes should be or if youâre likely to get some kinds of diseases.
You get your genes from your parents. They come grouped in long strands of DNA called chromosomes. Every healthy person is born with 46 chromosomes in 23 pairs. Usually, you get one chromosome in each pair from each parent.
Also Check: What Is Frontal Lobe Dementia
Whole Genome Sequencing Vs Genotyping Dna Tests
Traditional consumer DNA tests only provide data on up to 2 million data points, compared to the complete 6 billion analysed in a whole genome sequencing test. While this is sufficient for a basic overview of your health, fitness and nutritional data, many important factors go amiss.
A greater understanding of genetics has led to the realisation that the 98% of non-coding DNA once considered irrelevant, actually plays a hugely important role in regulating the coding portions of our DNA.
This means that if you want a comprehensive and accurate analysis of your entire genome, complete with reporting on rare and hereditary diseases, a whole genome sequencing test is your only reliable option.
What Does Pgd Involve
PGD involves the following steps:
Also Check: Is Dementia Inherited From Mother Or Father
What Does The Test Result Mean
People who have symptoms of Alzheimer disease and have one or more APOE e4 copies are more likely to have AD. However, it is not diagnostic of AD and should not be used to screen asymptomatic people or their family members. Many individuals who have APOE e4 alleles will never develop AD. Even in symptomatic people, only about 60% of those with late onset AD will have APOE e4 alleles.
Although APOE genotyping may be used clinically by Alzheimer experts, it can only provide additional information about a person with dementia. A definite diagnosis of Alzheimer disease can only be made by examining a persons brain tissue after their death.
Who Can Take A Diagnostic Genetic Test
To see whether genetic testing might be useful, the doctor will collect information on the persons medical history and that of their close family. If possible, the doctor will collect information on at least three generations of the family. The medical history will include details of:
- any family members diagnosed with dementia
- any family history of mental illness
- any family history of strokes or neurological conditions .
Diagnostic testing for familial dementia is only normally recommended if the person has developed symptoms very early on or if there is a particular familial pattern.
If the doctor does not find a strong family history of dementia, they will not recommend that the person take a diagnostic genetic test.
Predictive testing for dementia Predictive testing for dementia.
Read Also: What Is Happening To The Brain During Alzheimer’s
Genetic Testing For Alzheimers
Although genetic testing can detect both the APOE 4 gene and rare Alzheimers genes, most healthcare professionals do not recommend them for late-onset Alzheimers disease. This is because the presence of the APOE 4 gene does not guarantee the development of Alzheimers in an individual, weakening its position as a deciding risk factor. Genetic testing for APOE 4 is mostly done for research purposes. However, it may be appropriate for diagnosing early-onset Alzheimers disease.
Scientists believe that genetic testing may never predict the disease with absolute accuracy because several other factors are also involved in both its development and progression. For instance, an individual may have an increased risk of disease development even in the absence of the APOE 4 gene due to cardiovascular diseases, environment, or other lifestyle factors.
Genetic Causes Of Dementia
One rare form of Alzheimers disease is passed from generation to generation. This is called Familial Alzheimers disease . If a parent has a mutated gene that causes FAD, each child has a 50% chance of inheriting it. The presence of the gene means that the person will eventually develop Alzheimers disease, usually in their 40s or 50s. This form of Alzheimers disease affects an extremely small number of people probably no more than 100 at any given time among the whole population of Australia.
Three genes have been identified which, if mutated in certain ways, will cause FAD. These are called presenilin 1 , presenilin 2 and the amyloid precursor protein gene on chromosome 21.
Also Check: Does Hearing Loss Cause Dementia
What Is Alzheimer Disease 1
Alzheimer disease is an adult-onset progressive dementia. It is relatively common and the overall lifetime risk of developing dementia is 10-12%. Seventy-five percent of AD cases are sporadic, of unknown cause and usually have late onset of symptoms. Twenty-five percent of AD cases are familial and are composed of two types:
- Early-onset familial AD with a mean age of onset < 60-65 years
- Late-onset familial AD with a mean age of onset of > 60-65 years
Three genes have been associated with early-onset familial AD amyloid precursor protein , presenilin 1 , and presenilin 2 . Each of the identified genes is involved in production of the amyloid ß peptide, a major component of amyloid plaques. Early-onset familial AD follows an autosomal dominant inheritance pattern.1
While information about the genetic factors involved in late-onset familial AD is limited, this type of AD has been associated with apolipoprotein E gene variations. These are considered a risk modifier, especially APOE e4. Some data suggest that a young asymptomatic person with two copies of the APOE e4 allele may have an increased lifetime risk of developing AD and a lower age of onset of AD compared to persons who have only one or no copies of the APOE e4 allele. Approximately 20-25% of the general population carry one or more copies of the APOE e4 alleles.2 Approximately 42% of persons with AD do NOT have an APOE e4 allele.1 APOE e4 is neither necessary nor sufficient for the disease.3