When is it time to test for Huntington's disease?

January 27, 2018

For most people, getting a test result for Huntington's Disease is something that is given you in person. It is not something to be taken lightly and is normally completed after informed consent is given.  Informed consent usually includes genetic counseling to be sure the patient is aware of what the disease is, what it could mean to their family and the repercussions of a positive result.

 

Before this counseling, patients may undergo a series of tests including a general examination, a review of your family medical history as well as a neurological examination: (motor symptoms, sensory and psychiatric symptoms). 

 

A neurologist may also include Neuropsychological testing using standardized tests to assess memory, reasoning, mental agility, language function and spatial reasoning. From this, the patient may move on to a Psychiatric Evaluation to judge a number of factors including:  emotional state, patterns of behaviours, quality of judgment, coping skills, signs of disordered thinking and even evidence of substance abuse. A doctor may also order brain imaging and function through an MRI or CT scan which may not show evidence of Huntington's Disease in the early stage of the disease but could be helpful to rule out other conditions that may cause similar symptoms. At this point, the patient's doctor may refer them to genetic counseling where informed consent will be requested. Following receipt of consent, a blood sample taken is taken.

 

Once the blood is taken it will be sent to a genetics lab for testing. Once the results of the genetic test are received, the patient will be asked (again), if he/she still would like to hear the results. In the form pictured, it is interesting to note that the blood sample was received in 2010, but a result was not given until 2017.

 

This patient had agreed to a blood test, but when asked for informed consent which included counseling, they had refused which meant the test could not proceed. The test would not be granted until many years later, using the original blood sample, when the patient was deemed incompetent and was completely nonverbal by a psychiatrist. It is also apparent that this test result was positive, showing 17 trinucleotide repeats from the father (normal) and 46 repeats from the patient's mother.  So the patient has a CAG count of 46.  The clinical diagnosis also states that this patient, as well as family members, should be referred to genetic counseling. Patients should also remember that they are more than their CAG.

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