At a glance

Also known as

Chromosome Microarray testing; CMA testing

Why get tested?
Microarray testing is mainly used in medical practice to investigate children who have developmental problems
 
When to get tested?
When an infant is found to have developmental delay, intellectual disability, autism, or at least two congenital abnormalities and the cause is not apparent from the clinical findings
 
Sample required?
A blood sample drawn from a vein in the arm. Sometimes cells obtained through amniocentesis or chorionic villus sampling from a pregnant woman. Where it is technically difficult to obtain a blood sample (e.g. children with severe autism, young babies) a saliva sample can be used, however the failure rate is higher and it needs to be arranged with the laboratory prior to sample collection (see also: Coping with discomfort and anxiety - Tips to help children)
 
Confused about genetics?
See our Genetics Information page

 

What is being tested?

Microarray testing is a technique that is used for a wide variety of purposes. In diagnostic testing it is primarily used to test for the presence in the patient’s DNA (their genome) of either tiny missing sections (called microdeletions) or extra duplicated sections (called microduplications).
 
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm. Under special circumstances, a saliva sample can be used.
 
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
 

The Test

How is it used?

Microarray testing is more sensitive than conventional chromosome analysis, called cytogenetics or karyotyping. Although both are able to examine all chromosomes, microarray testing can detect very small changes that cannot be seen using a microscope.
 

When is it requested?

Microarray testing is ordered when someone – usually an infant – is found to have developmental delay, intellectual disability, autism, or at least two congenital abnormalities and a diagnosis of the cause cannot be made from the information available from clinical examination, imaging studies and other blood tests.
       

What does the test result mean?

The microarray most commonly gives a negative result which means that there are no missing pieces or additional pieces of DNA. If the microarray test does find that there is either missing or additional DNA (called copy number variants) the next step is to assess the significance of the results.

Not all missing or additional pieces of DNA cause problems. Some can be present in a person or multiple members of a family without causing any problems at all. The genetics specialists interpreting the test will look at the case reports to see if the changes found are known to be associated with the problems the patient is having. They will also take into consideration the genes known to be located within the copy number variant segment that has been found. In many cases the same results have been seen previously in other patients and the test result will allow the doctors to make a diagnosis. However, sometimes the significance of the changes found is unknown. This happens quite often because the human genome is enormous (it contains three billion base pairs) so there are many places for variations to occur. If a copy number variant of unknown significance is found, the parents of the child can be tested. If one of them has an identical variant in their DNA but does not have the medical problems found in the child, the variant is less likely to be the cause of the child’s problems.

What does the microarray not test for? 
There are several common conditions that will not be detected on the microarray test. These include:

Common Questions

How much does it cost?

In Australia the Medicare schedule will rebate microarray testing in a person, usually a child, with developmental delay, intellectual disability, autism, or at least two congenital abnormalities. Some laboratories may charge more than the Medicare rebate, so there may be an associated out of pocket expense. If the clinical information does not meet these guidelines, the cost may be about $600.
 

How long does the testing take?

Generally, a result is available within two months.
 

Last Review Date: November 1, 2019