HD Genetic Testing
What Is Predictive Testing in HD
Home | Index
What Is Predictive Testing in HD
 
The following is from the HD Center of Excellence at the  University of Virginia to give you a general idea of what is involved in the genetic testing for Huntington's Disease through an facility that abides by the Genetic Testing Guidelines established for HD.  
The identification of the HD gene allows individuals who are at risk to find out now whether or not they have inherited the HD gene. In most instances a blood sample from the at-risk individual who wants testing and an affected family member will be required to perform predictive testing.
 
In some cases it may be possible to test only the person who is at risk. This applies especially to those families in which there is only one individual diagnosed or where the individual wishing to be tested is adopted and does not have much information regarding his/her biological family.
 
The following example illustrates how predictive testing can be done in a family. Mary has requested predictive testing. Her father, John, has Huntington's disease. A sample of her father's DNA is analyzed and it is determined that he has 15 repeats on one number four chromosome and 45 repeats on the other.
 
 
The fact that he has a gene with more than 40 repeats supports the clinical diagnosis of HD. Mary's DNA can then be assessed.  If she has received 10 repeats and 45 repeats, the 10 must have come from her mother, Angieand the 45 repeats must have been inherited from her father.
 
This indicates that she has inherited the HD gene, and she will develop HD. If, on the other hand, she has inherited 10 repeats and 15 repeats, she received the gene containing the 15 repeats from her father. This is not the gene causing HD, and therefore she will not develop HD.
 
Predictive testing provides a highly accurate answer as to whether or not Mary has inherited the gene causing HD. It does not, however, say anything about  her current health with respect to Huntington's disease or when she might begin to experience symptoms.
 
In a small number of families, predictive testing may not be possible.  This may occur if the clinical diagnosis in the family is HD, but none of the affected individuals in the family demonstrate the increased number of repeats found in the HD gene.  This could happen because the family has been misdiagnosed and the disorder is not HD, or potentially because there is another change in this gene causing HD that we do not yet know how to detect.  
 
Another reason why testing could be uninformative is that the at-risk person may inherit a gene that has an "intermediate"  repeat size between 36 and 39. Such an intermediate, or equivocal, result occurs  infrequently.
 
THE PREDICTIVE TESTING PROGRAM
(At University of Virginia HD CoE)
 
The testing program usually involves several sessions. The following components are usually included:
  • An initial phone contact and a pre-screen interview with the at-risk individual
  • At least three pre-test, in-person sessions for genetic and psychological counseling, neurological and neuro-psychological evaluations. Additional sessions may be necessary if issues emerge that should be resolved before proceeding with the test. A blood sample for DNA testing may be drawn at the third visit or a subsequent visit. 
  • The next session is for disclosure of results. It takes about three to four weeks to get the results once the blood is drawn.
  • Post-test counseling sessions.
The time between each visit will depend both on the number of people who request testing at our center and on the length of time you choose between visits. The length of time needed to complete the protocol from the first visit to receiving results is commonly three to four months.
 
 
 
The same kind of predictive testing described above can be used in prenatal testing (testing of a pregnancy). There are three different situations in which prenatal testing for HD may be done:
  1. The expectant parent has HD.
  2. The expectant parent has had presymptomatic testing and has inherited gene for HD.
  3. The expectant parent is at risk and asymptomatic and does not wish to have predictive testing for
    himself/herself.
"Exclusion" prenatal testing may be offered to determine if the fetus is "excluded" as a gene carrier or if the fetus has the same risk as the parent (50%).
 
 
NEUROLOGICAL EXAMINATION
 
The purpose of the neurological examination is to make certain that the individual at risk for HD is not showing symptoms of the disease and actually is "presymptomatic." Every effort is made to distinguish the difference between a diagnosis of HD based on clinical symptoms and the finding that an individual is a gene-carrier. A person for whom a positive clinical diagnosis has been made may feel that he or she does not need testing. Another individual may want confirmatory testing.
 
A person with subtle dysfunctions may be at slightly increased risk of being a gene-carrier or may be relatively close to more overt symptomatology. The neurological exam can provide the HD team with information about how closely an individual may need to be followed after learning the test outcome.
 
For completely asymptomatic people who later find that they have inherited the gene for HD, the neurological evaluation also serves as a starting point for long-term follow-up and care.
 
 
Psychological screening, including neuro-psychological testing, is part of the protocol. If significant psychological problems are identified, it may be appropriate to delay testing and address these psychological issues first.
 
The risk of an adverse emotional response remains the single greatest risk of the test. It is important that the psychological evaluation of emotional stability not be viewed as a hurdle to be jumped in order to qualify for testing, but rather as a method of identifying persons likely to need greater emotional support in follow-up. In some instances, such as overt risk for suicide and/or major depressive symptoms, it is appropriate to delay testing, initiate psychiatric treatment, and become emotionally stabilized before proceeding with the test.
 
 
 
Regularly scheduled follow-up is a necessary and important part of testing. The psychological impact of a test result -- a good or a bad result -- varies considerably and it is difficult to predict what your response might be. The testing center works with the local counselor to provide the assistance needed.
 
 
The total cost for the visits, neurological and neuropsychological testing, and DNA analysis will be roughly $1500-2000. There are three options for payment. We will need to know which option you have chosen when you enter the program. The DNA analysis fee is about $220.
 
 
Payment Options
 
1.  You can submit all the fees to your insurance. You may want to find out anonymously if the insurance company will cover the cost of testing and evaluation without requiring information regarding the outcome of the test. This is a decision that may affect your health care coverage in the future, especially if you change jobs or your employer changes health plans. If you are in a managed health care plan, you may need preauthorization from your health care provider.
 
The fees for the neurological examination and genetic counseling are submitted with an insurance code for "Family history of a musculoskeletal disorder." Claims for physician visits because of a "family history" of a disorder are often not paid by insurance companies.

2. Submit the fees for the visits and examinations to your insurance company, but pay for the DNA analysis yourself, so that you are  not obliged to reveal the outcome of the test to your company.
 
3. You can pay the fees yourself. The University of Virginia Hospital  offers a sliding scale based on financial screening that may reduce the fees for individuals with limited incomes. In addition, the hospital will work with you on an extended payment plan, if needed.
 
Many people choose to pay for the testing themselves in order to protect their confidentiality to the greatest possible extent.  If they learn they have not inherited the gene, they may decide to submit the fees to insurance  for reimbursement of out-of-pocket expenses.
 
If you are considering this option, you should check with your company about the time within which reimbursement may be requested.
 
We are able to set up special payor accounts in the billing system for  individuals who elect to self-pay so that bills related to predictive testing are handled separately from other UVA accounts they may have. We feel this will offer another layer of protection of your confidentiality.
 
The cost of processing your affected relative's blood sample should be covered by your relative's insurance.
 
Long-term Care Insurance
 
We encourage everyone who enters the predictive testing program to consider applying for long-term care insurance before learning the results of the test.  This will permit you to answer all the questions on an application honestly since you will not know the outcome of the test.
 
Some applications include the question "Are you currently under medical advice  or treatment?" If you have already begun the testing program, the answer to  this would be "yes."
 
You may wish to apply for disability insurance at least  3 months before entering the program so that you can answer "no" well in advance of appointments with us.
 
 
 
If you are considering predictive testing, it is important to think carefully about what that information might mean for you and your family.   You will be learning something about your future - Are you going to develop HD or not? The answer to that question should never be forced on you.
 
This is a deeply personal decision that should be made only after you have had an opportunity to understand the technical and emotional aspects of predictive testing, and to balance the advantages and disadvantages of knowing whether you are likely to develop this disease.
 
Due to the complexity of this decision and the potential emotional impact of the results, testing is usually offered only to individuals 18 years or over.
 
Counseling is an important part of this process, both before and after you receive results of predictive testing. Before testing, counseling will focus on exploring reasons for taking the test and preparation for receiving results. After testing,counseling is geared to offering support and assistance in understanding the impact of the test results on your life and the lives of your family members.
 
The technological issues related to predictive testing have been introduced above. Your genetic counselor can review these and explain them more fully. He or she can also tell you what blood samples will be needed in your particular family, and whether testing will be possible for you should you decide to request it.
 
The emotional issues may be more difficult to address. The decision to have predictive testing is a big decision. Counseling can provide an opportunity to explore the reasons for having the test and the possible effects this testing will have on your life.
 
Here are some possible questions to ask yourself and to discuss with those close to you:

What does it mean for you to be at risk for HD?

How has it affected your life and your plans for the future?

Would this be different if you knew whether you are going to develop HD?

How will it make you feel if you are told you have inherited the gene for HD?

What will it mean for you if you have not inherited the gene for HD?

How will the results of the test affect other members of your family?

How have you coped with difficult times in the past?

Have there been stressful or difficult times in your life?

Are there people in your life who will help you cope?

Who will you tell about your decision to have predictive testing?

Who will accompany you when you receive the results of the test?

Would you want some time off from work after you receive the results?

Are you thinking about having children?

Would you like more information about the options available for testing a pregnancy for HD?

If you are considering a prenatal test, have you thought about what it might mean to you to learn that your fetus has inherited the gene for HD? Would you terminate your pregnancy under those circumstances? If you use the prenatal "exclusion" test, would you terminate your pregnancy if the fetus has an increased risk of 50%? Would you prefer to have your own predictive test prior to making a decision about prenatal testing?
 
Considering these questions in advance and thinking ahead about the possible effects of predictive testing may help you to decide whether to have predictive testing, and may reduce stress at the time you receive your results, should you decide to proceed.
 
Discussions with your family and friends, and with the HD team, may help you to decide whether predictive testing is something you really want to do. Only when the personal and technical issues are well understood should a final decision about testing be made.
 
 
Predictive testing should take place during a time of low stress in other areas of your life and in an environment that can provide adequate support. Except during pregnancy, testing should not involve a sense of urgency or emergency, and indeed should be considered in a cautious manner.
 
The fact that it is now technically possible to obtain test results in a few weeks rather than several months can have the effect of encouraging individuals to rush the process. However, having enough time to really think about the implications of testing is crucial, as evidenced by the number of individuals who drop out of the counseling process before actually having
the test done.
 
 
At the outset, you should identify a companion -- a spouse or a close friend -- to accompany you to all of the counseling and testing sessions. Another at-risk individual, such as a sibling, may not be a good choice as a companion.
 
Being present throughout, the companion will gain special insight into what you are going through and will thus become a uniquely valuable source of moral support.
 
Early identification of a counselor close to home is also recommended, particularly if the person taking the test lives some distance from the University Medical Center. The counselor may be a psychologist, social worker, psychiatrist, or another mental health professional. He or she should agree at the start to be available for emotional support and/or counseling at any time throughout the testing process. The counselor should have a consulting relationship with the HD team if at all possible. The HD team can help you find a counselor in your area.
 
 
DNA banking
Allows storage of samples of DNA for future use. This will ensure that samples will be available in case someone in your family wishes to have predictive testing in the future. If DNA has not been banked and crucial family members have died, predictive testing may not be possible in some situations.
 
It is very important that DNA samples are stored from those individuals who have HD. It may also be important in some families to bank the unaffected husband or wife of the HD patient (i.e., the person whose children are at-risk of HD). All information contained in the DNA bank is confidential. Samples may be stored indefinitely, and no results are disclosed to anyone unless specifically requested or authorized.
 
For the DNA bank to be useful, it is essential that the information contained in its records be complete and accurate. Additional information and assistance with banking are available at the University Medical Center.
 
I understand that there can be three outcomes to my test:
  1. Negative: I will be told that the CAG repeat size is in the normal range (35 or fewer repeats) and that I am not likely to develop HD.
  2. Positive: I will be told that the CAG repeat size is expanded into the HD range (40 or more repeats) and that I am highly likely to develop HD at some point in my life.
  3. Uninformative: I will be told that the CAG repeat size is in the intermediate range (36-39 repeats) and that it is unclear whether I will or will not develop HD at some point in my life.
Adapted from: Predictive Testing for Huntington's Disease, by the Huntington's Society of Canada and Guidelines for Genetic Testing for Huntington's Disease, (revised 1994) by the Huntington's Disease Society of America. Huntington's Disease Programs & Services at the HD Center of Excellence at the  University of Virginia