Why It Is Done

This test may be done to:

• Find out if you carry a gene for an inherited disease, such as Tay-Sachs disease or cystic fibrosis. This is called carrier identification. In families that have these diseases, some people don’t get the disease, but they carry a gene change that they could pass on to their children. Finding out if you’re a carrier can help you make decisions about having children.
• Find out if your fetus has a genetic disorder or birth defect such as Down syndrome. This is called prenatal testing. It can help you make decisions about your pregnancy.
• Check your baby for certain diseases, such as PKU. This is called newborn screening. This information can help guide treatment if your baby has a disease.
• Find out if you carry a gene that increases your risk for a disease later in life, such as breast cancer or Huntington disease. This is called late-onset disease testing. This may be important if a close relative has such a disease. The information might help you take steps to prevent the disease. Or it can help you make decisions about having children.
• Find out if you have an inherited heart disease called hypertrophic cardiomyopathy. You may want to have this test if a close relative has the disease.
• Check for genetic changes that may affect your treatment. Testing may help your doctor find out if a blood thinner will work for you. Or it can help your doctor suggest the best treatment for a disease such as HIV or some cancers.

How To Prepare

You do not need to do anything special to prepare for this test.

Talk with your doctor if you have any concerns about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).

The information found by a genetic test can have a huge impact on your life. So before you have the test, you may want to talk to a genetic counselor or a doctor who specializes in genetics (geneticist). Genetic counseling can help you understand your genetic risks and decide if you want testing.

How It Is Done

A genetic test can be done using almost any cell or tissue from the body.

Blood sample from a heel stick

For newborn testing, the blood sample is usually taken from the baby’s heel instead of a vein. The health professional doing the heel stick will:

• Clean your baby’s heel with alcohol. Then he or she will prick the heel with a sharp tool called a lancet.
• Collect several drops of blood inside circles on a special piece of paper.
• Put a small bandage on the site.

Blood sample from a vein

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure on the site and then put on a bandage.

Cell sample from a fetus

Cells are collected using amniocentesis or chorionic villus sampling.

How It Feels

Blood sample from a heel stick

Your baby may feel a little discomfort when the skin is pricked.

Blood sample from a vein

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Saliva, urine, or semen sample

It is not painful to collect a saliva, urine, or semen sample.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if you have a blood transfusion within a week before the test.

What To Think About

The information found by a genetic test can have a huge impact on your life. So before you have the test, you may want to talk to a genetic counselor or a doctor who specializes in genetics (geneticist). Genetic counseling can help you understand your genetic risks and decide if you want testing.

• A prenatal test may find a serious inherited disease or disorder (such as Down syndrome). This would greatly impact both you and your child. You may want to think ahead to what you might do if the test finds a serious problem.
• The results of the test are protected under the Health Insurance Portability and Accountability Act (HIPAA). HIPAA requires that providers, such as doctors, nurses, and hospitals, keep your health information private. Your privacy should be maintained, and your information should only be released to those who are authorized to have it.
• Finding out that you have a genetic disease should not affect your ability to get a job or get health insurance. In the United States, there is a law called the Genetic Information Nondiscrimination Act of 2008 (GINA). It helps protect people who have DNA differences. But it has some limits. For example, this law doesn’t apply to life insurance, disability insurance, or long-term care insurance. And it doesn’t protect people who work for companies with fewer than 15 employees.