This video will give you information about a genetic test called chromosomal microarray,
or array for short. Your doctor has suggested
this test to look for a cause for your or your child’s health or learning concerns.
In this video, we will talk about: What the array test looks for
What results you can expect from an array And limitations to this type of test
First, let’s review some basic genetics. At the centre of each cell in our body is
our genetic information. This is called DNA.
A gene is a section of DNA that gives instructions telling your body how to grow and function.
Your DNA is packaged into structures called chromosomes.
You have two copies of most chromosomes, and 46 chromosomes in total.
One copy comes from the egg and one from the sperm that formed you.
Because chromosomes contain our genes, the full set is important for growth and development.
An array is a test that looks for any pieces of chromosomes that are missing
and any pieces that are extra. An extra piece of chromosome is
called a duplication. A missing piece of
chromosome is called a deletion. These changes to our chromosomes can
sometimes cause health or learning concerns. It’s important to know that changes to our
chromosomes are not caused by something a person or parent did or did not do.
Sometimes, these can be new, random changes that did not come from a parent.
In other cases, they can be passed down from a parent to a child.
An array is done on a sample of blood. It can give four kinds of results:
Positive Negative
Uncertain Incidental
A positive result means that the array found a genetic cause for your or your
child’s health or learning concerns. Knowing the genetic cause of these concerns
can provide helpful information for you and your doctors.
Testing parents can also show how the condition may be passed down in a family.
A second possible result is that the array does not find anything.
This is called a negative, or an uninformative, result.
There could still be a genetic concern, but the array was not able to find it.
The third possibility is an uncertain result.
This means that the array found a change, but it is not well-understood.
The change may or may not explain your health or learning concerns.
Your healthcare team will talk with you about next steps to try to better understand this result.
Sometimes parents or other family members may be asked to provide a blood sample for more testing.
The fourth possibility is an incidental finding.
Because the array looks at all of your chromosomes,
it can sometimes find a genetic condition that is not related to your current concern.
This can be surprising to learn about. Although an incidental finding does not
explain your current health concerns, it may still be medically important for your family.
It is important to know that there are limitations to the array test:
Because this test only looks for missing and extra pieces of genetic material, some genetic causes
for health concerns cannot be found by this test. In some cases, your healthcare team might
suggest a more detailed test to look at your genes ‘up close’.
Your doctor has recommended a chromosomal microarray to find
a diagnosis or an explanation for you or your child’s current health or learning concerns.
If you have any questions about this test, please talk to your healthcare team!