What is genetic testing?

Genetic testing is a laboratory test that can help figure out the cause of a person’s health problem or condition by looking for genetic variations associated with a disease.

Humans have 20,000 to 30,000 genes that are passed from parent to child. Sometimes a person has a change or alteration in a gene that causes the gene not to work properly in the body. The non-working gene can cause a person to develop health problems or diseases.

The results of a genetic test can provide important answers about many health conditions. Genetic testing can confirm or rule out a suspected genetic disease and help medical teams determine the best plan to manage a patient’s care.

Types of genetic tests

Currently, most genetic testing is done by looking for changes in one or several genes at a time. Newer types of genetic tests offer a way to look at almost all of a person’s genes using a single test.

Gene sequencing

Gene sequencing reads through every letter of the gene to see if there are any changes or variants. Genetic counselors use this information to determine what sort of effect, if any, that variant has on the gene’s function.

• If we suspect a medical condition is caused by a change in a specific gene, we can test this particular gene. This is called single gene sequencing.
• Gene panels can sequence groups of genes that have been known to be associated with certain symptoms or diseases.
• All the genetic material in a person is referred to as their genome. Whole genome sequencing is a type of genetic test that looks at the sequence of all of the DNA in a person’s body. This test is not widely clinically available at this time.  
• The portion of the DNA that encodes a person’s body to make proteins is referred to as that person’s exome. The vast majority of known genetic diseases are caused by mutations in the exome. Whole exome sequencing looks at this portion of DNA.

Genome sequencing or exome sequencing is usually done to try to figure out the cause of a condition that seems to be genetic. It is often performed when there are many possible genes that could be causing a patient’s condition. It might also be performed when standard genetic testing has not identified the cause or a diagnosis.

Chromosome-based tests

Arrays

A chromosomal microarray (or array) is a type of genetic test that can detect changes in the number of genes. It looks for extra or missing portions of a chromosome, which may include one or multiple genes. The microarray looks for clues of what genes may be causing your child’s features. Microarrays are utilized frequently for people with developmental delay, autism spectrum disorder, or many other congenital anomalies. The types of genetic changes identifiable in a microarray are different than in genetic sequencing. Sometimes a person might get a microarray and a sequencing test.

Karyotypes

A karyotype is a visual representation of the chromosomes within a single cell. It is a way to look at the chromosomes with a microscope. A karyotype can detect major chromosomal differences, like extra or missing chromosomes, rearrangements amongst the chromosomes, or structural differences of the chromosomes. Down syndrome is an example of a disorder that can be detected by karyotyping

What to expect

The most common approach to genetic testing is to gather a blood or existing DNA sample from the affected individual. Less frequently, other tissue types (for example, skin cells or cheek swabs) are needed.

For some genetic tests, like exome sequencing, we also request blood samples from both biological parents. If biological family members are not available, the testing can still be completed.

How long does genetic testing take?

The turnaround time for genetic testing varies. Some test results are available in weeks, whereas others can take several months. The IMGC clinicians will discuss the approximate time it may take to receive results related to your specific test(s).

What happens after genetic testing is completed?

Depending on your and your referring clinician’s preferences, you may receive your test results from that provider or from the IMGC team. In either case, you will schedule a visit to learn the results and about what these results mean for you or your family members. This may include:

• Prognosis: What happens in the short and long term to others with the same condition
• Treatment: What medications, therapies or other management strategies, if any, are available to improve the outcome
• Recurrence risks: What is the likelihood that the same condition would happen to another family member
• Additional testing: What additional testing might be needed and how other family members can obtain testing

Will insurance cover genetic testing?

Insurance coverage for genetic testing and counseling varies widely. The IMGC works with financial counselors who are committed to helping you navigate the often-complicated insurance process. Visit our appointment preparation page for more information on how the IMGC can support you pre- and post-test.