Genetic Testing

Posted on May 17, 2013 in Young Adults

In 1993, scientists discovered exactly where the gene which causes Huntington’s disease is located in our DNA and figured out what it was doing. Because of this people are now able to have what is called a ‘predictive test’. It is known as a predictive test because the test can be taken by people at risk of Huntington’s disease who currently show no symptoms and want to learn whether they will develop the condition in the future. The result of this test will usually be able to tell a person whether they have the expanded gene or not.

It is important to note that if a person already has symptoms but has not been diagnosed, then a different approach would be taken which is known as ‘symptomatic testing’. This would involve that person going through a series of assessments with a doctor to confirm a diagnosis of Huntington’s disease and is quite different to ‘Predictive Testing’, which is what we are focusing on in this section.

The Science Behind Testing

You may hear people say that they ‘have the gene’ when referring to themselves as having Huntington’s disease. But the truth is, all humans have the gene that may cause Huntington’s disease – even those who never develop the condition. So if we all have the gene, why do some develop Huntington’s disease when others do not? The difference is people who develop symptoms of Huntington’s disease have a larger expansion of the gene than normal.

What is This Gene Expansion?

Without getting too scientific, there is a section, in the gene, which repeats itself over and over again. This is known as a ‘CAG repeat’ and each individual has a different amount of repeats. However, people with Huntington’s disease tend to have more repeats than usual, which means that the gene expands more than it should. This expansion can lead to Huntington’s disease.

The reason we are explaining CAG repeats is because of their relevance to predictive testing for Huntington’s disease. When people at-risk for Huntington’s disease have a predictive test, that person’s DNA is sent to a lab, and the clinical scientists will use special machines and lab techniques that will count how many CAG repeats that person has in the gene specific to Huntington’s disease. Once they know how many repeats a person has, they can tell if they will get the disease or not.

How Many CAG Repeats Will Cause Huntington’s Disease?

CAG repeats are split into four categories. If a person has less than 27 CAG repeats then they are what is called, ‘negative’ – meaning they will not get Huntington’s disease and they are not at risk of passing the disease onto any children that person has.

Someone who has 40 CAG repeats or more will definitely develop symptoms of Huntington’s disease in their lifetime (although it is not possible to say when symptoms will start) and the risk to any children is 50%.

If a person has between 27-35 CAG repeats, they will not develop Huntington’s disease, but there will still be a very small risk of that person passing on the disease to any children (the risk is about 5%).

Whereas somebody who has a CAG repeat between 36-39, would be in what is sometimes called the ‘grey area’, because it is uncertain whether they will develop symptoms in their lifetime or not.

Less than 27 CAG repeats

Negative – will not develop Huntington’s disease and children not at risk

27-35 CAG repeats

Negative – will not develop the disease but small risk to children.

36-39 CAG repeats

Positive – but may develop symptoms at an older age. 50% risk to children.

40+ CAG repeats

Positive – will develop symptoms in your lifetime. 50% risk to children.

Technically people in the 36-39 CAG repeat range do have the expanded gene, but people in this range may develop symptoms of Huntington’s disease at an older age. However, the risk of passing the expanded gene onto any children is 50%.

If you have been tested it is always important to be clear about the result of your predictive test. If you have any questions, or do not understand what the result has shown, do go back to the clinician who arranged your test.

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Genetic Counseling & Testing Process

Posted on May 17, 2013 in Young Adults

Testing is ultimately about finding out your CAG repeat—and this can be done with a blood test. But taking a predictive test in order to find out whether you will get Huntington’s disease or not is a huge decision to make in one’s life, and an enormous thing to deal with emotionally. What if a person gets a positive result? Would they be able to cope? Can they live positively with this news? These are questions that have to be asked, and that is why, before anybody can have a predictive test for Huntington’s disease, they should undergo genetic counseling. How long the counseling takes depends on you and your counselor, and your particular personal circumstances but generally it can take anything from 2-6 months. In that time many things are discussed, as one Genetic Counselor explains:

“It’s very much a two way process whereby you can explore the option of a predictive test and what it entails, including the possible test outcomes. There may be discussions around alternatives to testing, possible impact on other family members and the question of timing of the test. It can vary how ready an individual feels to proceed with a test—and that’s fine—we’d want to take it at a pace that feels right for the individual.”

Tiffany, Genetic Counselor

To begin the testing process you usually need to speak with your doctor, who will then put you in contact with your local genetics department. In order to be tested you normally have to be at least 18 years old – although if you are under 18, you can still speak with a genetic counselor about what a test involves and any other issues you may have with regards to Huntington’s disease.

If at any stage during the counseling process you change your mind and do not want to be tested, you can stop the process straight away. Some people even get all the way to having their blood taken and decide now is not the right time for them to hear their results, so they ask for their results to be kept under lock and key until they feel ready to collect them. The doctors and genetic counselors will not read your results until you’ve decided to receive the news.

It Is Your Choice

It is very important to remember that testing is a personal choice – a choice only you have the right to make. Some people in your life may tell you to test or not to test. But it is not up to them at all – it is entirely your decision and you should only get tested if you are sure this is what you want.

There is no right or wrong answer when it comes to making a decision about testing. We all live different lives and we all make different decisions. Some will choose to test (& will vary at what stage in their life they choose to do so), others will not – there are perfectly good reasons for deciding one way or the other. Although it is your decision, you may also wish to discuss your feelings with those closest to you (like a partner) for whom the result will also have a bearing. But ultimately it is your choice.

Emotional Aspects of the Testing Process

Aside from the practical ways to be prepared, testing is also a very emotional process from start to finish. From making the decision to test, going to your genetic counseling sessions, having your blood taken and receiving your result – each stage provides its own emotional hurdles to overcome.

Dealing with the emotions of testing is incredibly challenging for anyone. When you take into account that the whole process can take months, it can become very difficult for a person to maintain their calm throughout. You may have many ups and downs during the process, don’t be alarmed by this, it is quite normal and you should keep discussing your emotions with the genetic counselor (that is what they are there for). You could also seek advice from others who have gone through the testing process for Huntington’s disease already and have faced the same emotions and difficulties.

The Waiting Period

There is a part of the testing process that has not been highlighted yet, ‘the waiting period’. This period covers the time between having your blood sample taken and receiving your test results. People have to wait for weeks in-between their blood being taken and their test results appointment. Just how long that wait is depends on where you live and the clinic you are using. But this can be an incredibly difficult time for a person in the testing process; those weeks can often feel like months! People can become very anxious during the waiting period and it is important to try and stay busy during this time.

If you feel it would be helpful to speak to your genetic counselor during this period do call them (they will not know your result at this stage). Or again, seek advice and support from those who have experienced the waiting period themselves – this can be quite comforting.

Preparing for Your Results

Preparing for results is another challenging aspect of the testing process. Many people tend to develop a ‘feeling’ one way or the other about whether they are going to test positive or negative. Obviously you can’t guess or ‘feel’ what result you are going to get, and these guesses can end up causing more shock when you receive your results (should you get the result you weren’t expecting). It can often be good just to remind yourself during the process that until you test you are ‘at-risk’, rather than trying to guess one way or the other. However, preparing for your results can be useful and during your counseling you may be asked to think about what you will do if you test positive or negative. This is a good exercise because it allows you to really think and plan how you will react to your results, whatever they may be.

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Support

Posted on May 17, 2013 in Young Adults

Support during the testing process is not only important but can be very comforting. You are entitled and encouraged to bring along a family member or a friend to both your counseling sessions and your results appointment – and it is highly advised that you do so. Some people, when they decide to get tested, are hesitant to tell their family/friends, and decide to face the process alone. People’s reasons for not telling their family about such a huge life decision are usually because they do not want to put their loved ones through any extra stress, worry or pain – people want to protect their family. It is an understandable reason for keeping the process quiet; after all, many people testing have families that are already dealing with Huntington’s disease and people often feel like they are burdening their family by adding the testing process to the list of things to cope with. But it is unlikely to help you in the long run to keep this to yourself. As has been highlighted, testing is an incredibly emotional journey – you will need support during this process. Do not face it alone if there is no reason to – this is hopefully a time for the family to all get behind the person testing and support each other.

For people testing who have siblings either at-risk, already tested or symptomatic, testing can be an even tougher experience. Imagine testing negative if one of your siblings had already tested positive – how do you tell them your news? This is often called ‘sibling guilt’ and it can be uncomfortable and difficult to handle.

Support is the key, whatever the results as siblings you should use this as an opportunity to become closer and even more supportive. Talk about the worries you have with your siblings, express your concerns about how the family will react to your results before you get them – be prepared as a family.

However, you shouldn’t feel that you need your family’s permission or support to get tested – remember, it is your choice. There are other sources of support for you that you can reach through your national Huntington’s society of Canada or your genetic counselor.

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Getting Your Results

Posted on May 17, 2013 in Young Adults

Positive or negative, the day you receive your result may feel like the most surreal day of your life and it is important that you take the time to accept your result. The process of acceptance can only be done gradually over time. Both results will bring with them different emotions and different hurdles in the future. Testing positive raises some more obvious issues, but testing negative also has its complications for people. Both are discussed in the sections below. 

Testing Positive

Testing positive for Huntington’s disease is often a traumatic experience – one that can really knock you off your feet. Do not be surprised if it takes you many months to feel like yourself again, these things do take time and it is important not to expect too much from yourself after your result. As was highlighted in the main testing section, accepting your results can only be done gradually over time. It is important to remember that you are able to have follow-up appointments with your genetic counselor anytime you want to discuss your result and how you feel. This can be very useful and the counselor will be happy to go through any issues that are on your mind.

You also need to think about who you are going to inform about your results. Telling friends or work colleagues is really only something you can decide upon. The lack of understanding about the disease can cause issues, will they understand? Will it affect how people view you at work? Etc.

However, once you have had time to get used to the result, you can use the fact you have tested positive as the reason/motivation to do the things in life that you have always wanted to do. Why not go traveling, or change your career, begin a new fitness regime or have a fresh new start in life! Testing positive can be great motivation to get out there and experience life. Again, it may take time to find that motivation, but once you have it you can really make the most of things.

Another important issue to remember is that testing positive may change the way you see things in life. For instance, if you have a family member who is symptomatic with Huntington’s disease, you may find that, because you have tested positive, it is hard for you to witness that person’s progression. Time really does help, and you may not feel like you have a lot of it right now, but be assured you still have plenty of time to enjoy life. Research into Huntington’s disease is progressing really quickly and there is very much real hope for the future. You may want to help by participating in research yourself, it can be a very rewarding experience and many feel they are being productive by participating in research studies.

There are many good days yet to experience, and yes, you will have your bad days too (who doesn’t). But stay positive and keep moving forwards and you shall continue to achieve in life. Remember that you have always had the expanded gene; the only difference is that you know this now. You have the advantage of future knowledge about your life, use it. Testing positive might just be the motivation you needed to achieve great things and to lead a life to be proud of.

Testing Negative

Testing negative is generally seen as the ‘good result’, but people can be too quick to congratulate you on testing negative. They may expect you to be happy, delighted, or ecstatic. When in fact, testing negative does not mean somebody is completely free of Huntington’s disease from their lives. The chances are you still have family members who are either symptomatic, at-risk or gene positive – so the worry still remains.

One of the biggest issues for those that test negative is the guilt. So many people feel huge amounts of guilt for receiving a negative result – you may be feeling that way too. It is important that you discuss these feelings with your family and friends, be open and honest – you have every right to highlight your feelings.

Some people feel like a part of them has been taken away when they test negative – as if Huntington’s disease was a part of their identity, and now it has gone they are unsure what they want to do in life. Feeling this way may cause issues. For instance, one of the main things, for so many years, a person has in common with their family is Huntington’s disease, so if someone tests negative and now knows they won’t have the condition, they may feel a form of separation from their family – like they have lost that connection.

It is very important that you discuss any issues you are worried about. You are entitled to have follow-up appointments with your genetic counselor to talk about your result and any issues you have. But as was highlighted before, discuss your feelings with your family as well – they may not realize how you are feeling inside. You can only support each other if you understand the reason why support is needed – that means you need to be open and honest about your feelings with regards to testing negative, do not keep them hidden away purely because you got a ‘good result’ and feel you should not be complaining.

Finally, even though you may have tested negative, you can still help with the search for the cure. There are research studies that want and need people who have tested negative. You can participate in these and do your bit to help not only your family, but others suffering with Huntington’s disease too.

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Having Children

Posted on May 17, 2013 in Young Adults

Knowing that you are at risk of Huntington’s disease may have an impact on whether you decide to have children or not. The decision to have children is a very personal choice between you and your partner. This section looks at some of the options available with regards to having children.

The Genetic Risk to Children

The risk of passing on Huntington’s disease is usually the main concern when people at risk are thinking of having children. A lot depends on whether the person wanting children knows their gene status or not. Some people decide to test before they have children in order to find out whether there is a risk of passing the disease on to their children.

A person with a Huntington’s disease affected parent has a 50% risk of having inherited the Huntington’s disease gene. Each child of that person has a 25% chance of inheriting the condition. But this ‘25%’ only applies while the person is untested.

If a person has been tested and received a negative result, meaning they will not get Huntington’s disease, then that person will not pass on the risk of inheriting the condition to children. However, if a person has tested positive, meaning they will develop Huntington’s disease at some point in life, then each child will have a 50% risk of inheriting the condition.

Making Decisions

Having children is a passionate and emotional issue that often causes debate amongst families affected by Huntington’s disease. People may not agree with the decisions others make, but it is important to remember that everybody has a right to make their own mind up and make their own decisions in life.

Some people take the stance that they will never have children because they do not want to have a child at risk or have that child grow up in a family affected by Huntington’s disease. Other people go ahead and have children at risk, because there is a chance the child will not have the expanded gene, or they feel there will be good treatments or even a cure available by the time the child grows up.

Others want to have children, but want to reduce the risk of them inheriting Huntington’s disease. Technology and science has made this more of a possibility, and there are a number of options available that may provide a child free of the risk of Huntington’s disease.

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Family Planning: The Options

Posted on May 17, 2013 in Young Adults

 

  1. Having Children Naturally
  2. Prenatal Testing
  3. Exclusion Testing
  4. Preimplantation Genetic Diagnosis (PGD)
  5. Egg/Sperm/Embryo Donation
  6. Adoption/Fostering

 

1. Having Children Naturally

Although a lot of this section focuses on the options of having children without the risk of Huntington’s disease, it is important to highlight that having children at risk is an option too. Many people have children at risk for various reasons. A person may feel that with Huntington’s disease research going very well, that there will be good treatments, or even a cure, by the time the child grows up. Another reason people have children at risk is the fact there is always a chance the child will not have the expanded gene and will never get Huntington’s disease.

Some people may want to have a child without the risk, but feel that the options to do that are not available to them – this could be as a result of fertility techniques not being available in their country, a lack of financial support or a religious belief for example.

Having children at risk is something that often causes debate amongst families affected by Huntington’s disease. People may not agree with the decisions others make on this issue, but it is important to remember that everybody has a right to make their own choices and decisions. That decision, like any on this topic, should be respected.

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2. Prenatal Testing

Prenatal testing involves testing a fetus (unborn baby) around 10-15 weeks into a pregnancy to see if it has the expanded gene that causes Huntington’s disease.

Prenatal testing is usually only done when a couple is certain that they’ll terminate the pregnancy if the genetic test is positive. That decision has to be made beforehand. That’s because testing a pregnancy, but not going ahead with a termination after a positive test result, would take away the child’s right to choose whether to have the genetic test, later in life.

If the fetus does not have the expanded gene, then there is no risk to that child and the pregnancy can continue as normal.

If prenatal testing ends with a positive genetic test result, and a termination, then that person/couple could try again and hope that the next pregnancy produces a fetus with no risk of Huntington’s disease.

Prenatal testing can be done for those where the affected parent already knows their Huntington’s disease status, meaning they have tested and received a positive result.

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3. Exclusion Testing

Exclusion testing involves testing a fetus (unborn baby) around 10-15 weeks into a pregnancy to see if it has the tracking marker for Huntington’s disease. It is essentially the same process as prenatal testing but with a couple of key differences.

One difference between prenatal and exclusion testing is that exclusion testing is specifically for people who want to remain untested, but want to have a child without any risk of passing on the condition to them.

Exclusion: The Process

The other difference between exclusion testing and prenatal is that exclusion testing takes samples from three people, as opposed to two. Exclusion testing involves taking a blood sample from the fetus, the person at risk of Huntington’s disease and that person’s affected parent (the fetus’s grandparent). This can be a problem as you may not be able to get a blood sample from your affected parent for a variety of reasons. The affected parent’s sample is key to the whole process, as the extra sample is used to link and trace what genes the fetus has inherited.

Exclusion testing focuses on the section of DNA that contains the Huntington’s disease gene, and tries to show whether or not the fetus has inherited that section from the affected grandparent. If the fetus has not inherited it, then the risk of Huntington’s disease is very low. However, if it has inherited it, then there is a 50% risk to the fetus.

The major problem with exclusion testing is that it doesn’t reveal whether the fetus has inherited the healthy gene or the expanded gene – only whether or not it’s inherited the stretch of DNA from the affected grandparent or not. This is to protect the person at risk who does not want to learn their own status during this process. So, exclusion testing cannot be as precise as prenatal testing.

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4. Preimplantation Genetic Diagnosis (PGD)

PGD is a procedure in which a woman’s eggs and her partner’s sperm are taken and fertilized in a laboratory. From this, embryos are then formed and these embryos are tested to see if any carry a risk of Huntington’s disease. Only the embryos that do not have a risk of Huntington’s disease will be implanted back into the woman’s womb, where the hope is a pregnancy will follow. The success rate is quite low (around a 1 in 3 chance of a pregnancy) as the cycle can be affected by a range of factors including how the woman responds to the drugs, the number of eggs fertilized, the number surviving the test and the number with the expanded Huntington’s disease gene. Once the embryo has been implanted, the chances of success increase to 1 in 2. If the procedure is successful then the child will be born free of the risk of Huntington’s disease. Any remaining unaffected embryos can be stored for later use if required.

The PGD process can be a lengthy and emotional journey, with the woman having to undergo various tests and procedures, which can be strenuous at times. There may also be a lot of traveling involved to have the treatment and some may have to take time off work. In addition, failed attempts may be difficult to with cope emotionally. But for those that come out of the process with a successful pregnancy, PGD can be a very worthwhile option. Also, success rates tend to be slightly higher with couples from a Huntington’s disease family, due to most of the couples being younger when they request PGD.

Who is PGD available to?

PGD can be done by either those who have tested positive or those at risk. For someone who is untested, the process can be done without that person having to learn their Huntington’s disease status – using techniques similar to exclusion testing, described above. Again, this requires getting blood samples from the affected parent of the person going through PGD – although this is not always necessary. This is usually called exclusion PGD, or non-disclosure PGD.

PGD is also not available everywhere, with countries like Austria, Switzerland, and Ireland banning PGD for religious, ethical and moral reasons. Again, speak with a genetic counselor to see whether PGD is available in your country.

How much does PGD cost?

The procedure is expensive if there is no financial support available. The cost is somewhere in the region of US $15,000 for each attempt. Health insurance usually does not cover the cost of PGD. However, in some countries, like the UK, the public health care system may fund one or two PGD attempts, but even this can vary within individual countries, and sometimes may be limited to couples with no existing children. As you can see, financial support tends to vary quite substantially, so if you are interested in this option, speak with a genetic counselor or a health care specialist first about any financial support that may be available to you.

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5. Egg/Sperm/Embryo Donation

This method uses a donated egg or sperm in place of that of the affected parent – meaning the child will be free of risk from Huntington’s disease. Embryo donation is also available. The process is done through a qualified donor clinic. Pregnancy success rates vary between clinics but can be as high as 50%.

The downside of taking this route is that the affected person will not be the genetic parent of the child, which may be an issue for you and your partner, but you will still get to carry the baby through pregnancy and be able to impact on his or her life biologically and environmentally from the very beginning without passing on Huntington’s disease.

Also, at some point the child will need to be informed that the affected person is not their genetic parent and why this is the case. Statistics show that 1 in 3 children born through egg/sperm donation want to know who their genetic parent is once they are grown up. Depending on which country you have had your treatment, information about their genetic parent will be available via the donor bank. Some donors are what they call ‘non-anonymous’, meaning that their information is available should the child want to contact them later in life. Other donors are anonymous and contact cannot be sought in the future. Whether the donor is anonymous or not can depend on the rules of the country the procedure is being conducted in. Procedures vary in different areas, so be sure to check and discuss what is available in your area. Again, this is something that you will need to discuss as a couple if you want to go down this route, but support may also be available through organizations such as the Donor Conception Network.

Who can use the egg/sperm/embryo donation option?

The egg or sperm donation option can be used by anyone (at risk or tested). The egg/sperm donors themselves are screened and tested for genetic conditions, to avoid inheriting any conditions from a possible donor. So the risk of the child developing Huntington’s disease or any other genetic condition is extremely low. Again this can be an expensive option if funded privately, but may be cheaper than PGD depending on your clinic.

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6. Adoption/Fostering

Adoption is when a couple or a family take in a child who may have come from a difficult background, has been taken into care and needs a family to look after them. Adoption is generally considered an option for those wishing to have a child free of the risk of Huntington’s disease.

However, the downside is that couples at risk of Huntington’s disease may find it difficult to adopt, because of the fact the disease is in their family. At the beginning of the adoption process an assessment is done on every couple/family wanting to adopt a child, and each situation is carefully considered for the child’s sake. The adoption agency want to make sure that the child has a stable home to go to, and the risk that one of the parents could have Huntington’s disease can be seen as too much of a chance for them to take. But each case is assessed individually so do not rule out adoption straight away. It is certainly worth looking into and discussing with your local adoption agency, a genetic counselor or another health care professional in your area.

You may find that your adoption agency does introductory sessions that you can attend without making any firm commitments to adopt. They will be able to tell you more about both adoption and the potential impact of Huntington’s on your prospects of adopting. You may also be able to meet parents who have adopted in the past, who can tell you about their experiences and answer any questions you might have.

Depending on the country you live in, adoption can be a long process, as it takes time to go through the preliminary assessments, workshops and formalities before matching can begin. The time taken to match will depend on your requirements and theirs, how many children you are looking to adopt, what ages you would consider etc.

Fostering is also an option, even if you have been turned down for adoption on the basis of the future risk of Huntington’s disease. You may still be eligible for fostering because it is a more short term option caring for children for weeks or months at a time. Again, discuss this with your local adoption agency, a genetic counselor or another health care professional in your area to find out more.

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