Chromosome Microarray

Is Testing Right for Me? I Have My Test Results

Chromosome Microarray

Interpreting Chromosome Microarray Results

The results of chromosome microarray (CMA) testing are not always easy to understand. Sometimes, this test uncovers a change known to cause development problems, such as developmental delay or mental retardation. Other times, it shows uncertain results which require further testing of multiple family members to understand.

Although CMA is very sensitive and cutting-edge technology, it is not flawless. It can miss certain types of chromosomal changes. Many genetic syndromes require very specific DNA testing to diagnose. CMA doesn't find every possible genetic mutation in every gene. Therefore, a normal result does not rule out an underlying chromosomal or genetic condition. It simply means that there aren't deletions or duplications of DNA that can be found. Today's technology may not be advanced enough to provide an answer in some cases.

Possible Results

There are three types of possible results from a CMA test: positive, uncertain, and negative.

CMA Result Need to Test Family Family Study Results Meaning for Child Being Testing
Positive
Known chromosomal syndrome
Rare N/A Diagnostic
Uncertain
Chromosomal change found but not known
Yes Normal
or
Same change found
Likely diagnostic
or
No diagnosis found
Negative
No chromosome change found
No N/A No diagnosis found

 

Positive Result

With a positive result, the test revealed a chromosome change either known or expected to cause developmental problems. This result explains the reason for a person's health and/or developmental concerns. When other people with the same or similar result have been studied, the result provides specific medical information for the patient, family, and doctor. It may also help figure out if there are possible risks for future pregnancies.

Depending on the type of change found, your doctor may recommend that other family members have testing. Such follow-up testing is not common when the results are clear, but in some situations, can help determine if the chromosomal change found was passed from a parent (inherited) or new in that person. It can also help doctors clarify the meaning and significance of the results.

Although a positive test result may provide a diagnosis, many genetic syndromes have a wide range of effects on a person's appearance, medical problems, and mental functioning. No testing, including CMA, can predict how mildly or severely a person may be affected by a specific genetic condition.

Uncertain Result

With an uncertain result, the test revealed a chromosomal change that doctors and scientists don't know exactly how to interpret. These types of changes either have never been seen before in a patient, are very small, or are thought unlikely to cause any developmental problems.

These changes are referred to as "variants of unknown significance." In such cases, additional samples from parents or other family members may be needed to get a more complete answer. If family members have the same chromosome change but don't have any health or developmental problems, then the chromosome change is probably a normal variation and not disease-causing. However, if the chromosome change is not shared with normal, healthy family members, it may be more likely to be the cause of the patient's problems.

Sometimes, even after family studies, it is still not clear whether the test result is the cause of the patient's medical problems. Doctors may be able to do research to find out whether the change has been reported in other people and how they were affected by it. However, there are times when a clear answer can't be reached, even with extra testing and research.

Negative Result

With a negative or "normal" result, the test did not show any chromosomal changes that could be found on CMA. This could be because there really is no chromosomal change present or because there is a DNA or chromosomal change not detectable by the test. A genetic cause for the developmental problems can't be ruled out. There may be other changes in genes or chromosomes that can't be found with this testing. There are hundreds of known genetic syndromes that are not checked for with this test.

It may be useful for patients who have a negative CMA result to see a specialist in genetics for a full exam and further testing, if indicated.

Next: Pros & Cons

Why are you considering testing?

I am considering testing for my child who has signs and symptoms of developmental delay and/or autism, but hasn't been diagnosed for sure yet.

I am considering testing for my child who has developmental delay, mental retardation, birth defects and/or other unusual physical features without a known cause.

I am considering testing for my child who has an autism spectrum disorder.

I'm pregnant and considering testing because of birth defects found on ultrasound.

I lost a pregnancy (miscarriage or stillbirth) with birth defects.

None of these.

Chromosome microarray (CMA) testing and other genetic testing can be part of the evaluation for developmental problems, but it isn't the first step.

Evaluations may be needed with doctors and sometimes other specialists to decide whether your child has a health or learning problem. There are many different causes for developmental problems. Doctors need to consider the big picture, and review your child's birth history, medical history, do a head-to-toe exam, and decide what testing might be needed.

Chromosome microarray testing may be useful for your child.

About 10% to 20% of children with mental retardation/intellectual disability, developmental delay, birth defects and other unusual features have a chromosome change that can be found with this testing.

If a chromosome change is found, it is the likely cause of your child's problems. Testing is very accurate. Having information about your child's specific deletion and/or duplication can help guide healthcare decisions. Testing may be useful for other family members (including you as the parent) who are concerned about their reproductive risks.

If no chromosome change is found, a genetic cause of your child's problems can't be ruled out. There may be other changes in genes or chromosomes that can't be found with this testing. There are hundreds of known genetic syndromes that are not checked for with this test.

It is possible to get results from testing that are uncertain. Sometimes chromosome changes are found, and they've never been found before or it's not clear whether they have an effect on development. In order to get more information, testing may be done on both parents to decide whether the change was inherited or is new. Doctors may be able to do research to find out whether the change has been reported in other people and how they were affected by it. However, there are times when a clear answer can't be reached, even with extra testing and research.

Chromosome microarray testing may be useful for your child.

About 7% to 10% of children with autism will have a chromosome change found with testing.

If a chromosome change is found, it is the likely cause of your child's problems. Testing is very accurate. Having information about your child's specific deletion and/or duplication can help guide healthcare decisions. Testing may be useful for other family members (including you as the parent) who are concerned about their reproductive risks.

If no chromosome change is found, a genetic cause of your child's problems can't be ruled out. There may be other changes in genes or chromosomes that can't be found with this testing. There are hundreds of known genetic syndromes that are not checked for with this test.

It is possible to get results from testing that are uncertain. Sometimes chromosome changes are found, and they've never been found before or it's not clear whether they have an effect on development. In order to get more information, testing may be done on both parents to decide whether the change was inherited or is new. Doctors may be able to do research to find out whether the change has been reported in other people and how they were affected by it. However, there are times when a clear answer can't be reached, even with extra testing and research.

Chromosome microarray testing may be useful for your pregnancy.

Overall, about 1% to 3% of pregnancies with birth defects have abnormal test results on chromosome microarray (CMA) when regular chromosome analysis results are normal. Testing may provide you an answer about the cause of the birth defects in your pregnancy. It may give you some answers about what you might anticipate for the future.

If a chromosome change is found, it is the likely cause of birth defects in your pregnancy. Testing is very accurate when a chromosome change is found. Having information about the specific deletion and/or duplication can help guide healthcare decisions. Testing may be useful for other family members (including you as the parent) who are concerned about their reproductive risks.

If no chromosome change is found, a genetic cause of birth defects in your pregnancy can't be ruled out. There may be other changes in genes or chromosomes that can't be found with this testing. There are hundreds of known genetic syndromes that are not checked for with this test.

It is possible to get results from testing that are uncertain. Sometimes chromosome changes are found, and they've never been found before or it's not clear whether they have an effect on development. In order to get more information, testing may be done on both parents to decide whether the change was inherited or is new. Doctors may be able to do research to find out whether the change has been reported in other people and how they were affected by it. However, there are times when a clear answer can't be reached, even with extra testing and research.

If not already done, your doctor may also order a chromosome analysis (also called a karyotype). Around 16% to 30% of pregnancies with birth defects have a larger chromosome change that can be found with that testing. Chromosome analysis sees the "big picture" while CMA finds smaller changes. These two tests each have their benefits and limitations, so doctors use these tests in different ways.

If you've already had prenatal testing done by chorionic villus sampling (CVS) or amniocentesis, you probably won't need to have another procedure done to have CMA testing. Most of the time, the laboratory that handled the original sample can send cells for CMA, if they don't perform the testing themselves.

Chromosome microarray testing may be useful for you.

Testing may provide you an answer about the cause of the birth defects in your pregnancy and whether there is a higher chance for it to happen again. Chromosome microarray (CMA) is usually only done when birth defects are found because pregnancy losses for other reasons are common.

If a chromosome change is found, it was the likely cause of birth defects in your pregnancy. Testing is very accurate. Having information about the specific deletion and/or duplication can help provide an understanding of what caused the birth defects. Testing both parents will be useful to give accurate recurrence risks.

If no chromosome change is found, a genetic cause of birth defects in your pregnancy can't be ruled out. There may be other changes in genes or chromosomes that can't be found with this testing. There are hundreds of known genetic syndromes that are not checked for with this test.

It is possible to get results from testing that are uncertain. Sometimes chromosome changes are found, and they've never been found before or it's not clear whether they have an effect on development. In order to get more information, testing may be done on both parents to decide whether the change was inherited or is new. Doctors may be able to do research to find out whether the change has been reported in other people and how they were affected by it. However, there are times when a clear answer can't be reached, even with extra testing and research.

If not already done, your doctor may also order a chromosome analysis (also called a karyotype). Chromosome analysis sees the "big picture" while CMA finds smaller changes. However, it is sometimes technically difficult to do chromosome analysis on a sample from a pregnancy loss or stillbirth. If chromosome analysis can't be done, CMA can be done alone and still provide useful information.

Depending on the circumstances of your pregnancy loss, fetal autopsy may also be an option. A complete autopsy can often provide answers about the likely cause of birth defects, even if genetic testing is normal.

Chromosome microarray testing may not be useful for you. The main reasons for testing are listed in the Who Should Consider Testing? section.

CMA testing is sometimes used for other health problems, especially cancer. Those uses are not covered by this tool.

If you have a reason for testing that isn't covered here, talk to your doctor or a genetic counselor about whether testing might be useful for you.