Genetic Testing and Screening

Test Overview

A genetic test checks the DNA of your cells. It can find changes in your genes, or it can check the number, order, and structure of your chromosomes. Testing may be done on samples of body tissue, blood, or other body fluids such as urine or saliva.

You inherit half of your genetic information from your mother and the other half from your father. Genes determine things such as your blood type, hair color, and eye color, as well as your risk for certain diseases. Testing can find gene or chromosome changes that may cause medical problems.

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 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 condition 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.

Genetic testing can be used to find out the identity of a child's father (paternity). It can also be used in crime scene investigation.

How To Prepare

You do not need to do anything special to prepare for most of these tests. Your doctor will tell you how to prepare if you are having an amniocentesis or chorionic villus sampling.

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.

The information found by a genetic test can have a big 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

A heel stick is used to get a blood sample from a baby. The baby's heel is poked, and several drops of blood are collected. Your baby may have a tiny bruise where the heel was poked.

Blood sample from a vein

A health professional uses a needle to take a blood sample, usually from the arm.

Cell sample from a fetus

Cells are collected using amniocentesis or chorionic villus sampling.

Watch

How It Feels

Blood sample from a heel stick (usually done on babies)

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

Blood sample from a vein

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Saliva, urine, or semen sample

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

Risks

Blood sample from a heel stick

There is very little chance of a problem from a heel stick. A small bruise may form at the site.

Blood sample from a vein

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Saliva, urine, or semen sample

Collecting a saliva, urine, or semen sample does not cause problems.

Other risks

The information from a genetic test can affect you and your family in many ways. For example, it may have an impact on:

  • Your emotions and relationships. You may feel anxious or depressed if you learn that you are likely to have a serious disease or have a child who has a disease. This news may also affect your relationship with your partner or other family members.
  • Your treatment choices. If you test positive for a disease-specific gene change (mutation), you may decide to use preventive or treatment options, if they are available. They can help to reduce the impact or severity of the disease. While many treatment options have been proven to work well, others may be harmful or may not work.
  • Your pregnancy decisions. Genetic testing can help you make decisions about your pregnancy or plan for the future. If you find out that your fetus has a genetic disease, you may decide to end the pregnancy. Or you may change your delivery plans. If your baby is likely to need special care after birth, you may need to deliver in a hospital that can provide this care.
  • Your privacy. Many people worry that their genetic information might affect their job options or their ability to get insurance. But the United States has a law called the Genetic Information Nondiscrimination Act of 2008 (GINA). GINA prevents employers and health insurance companies from using a person's genetic information in employment or coverage decisions. This law does not cover life insurance, disability insurance, or long-term care insurance.

Genetic counseling is recommended before you have genetic testing. It can help you understand and make decisions about testing.

Results

The results of genetic testing depend on the type of test done. For example, the results may show if you have a genetic condition, how likely it is that you will have a genetic condition in the future, or if you are a carrier for a condition. The results of prenatal genetic screening may show how likely it is that your fetus will have a genetic condition or birth defect.

Credits

Current as of: July 17, 2020

Author: Healthwise Staff
Medical Review:
Kathleen Romito MD - Family Medicine
Martin J. Gabica MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Elizabeth T. Russo MD - Internal Medicine
Adam Husney MD - Family Medicine
Siobhan M. Dolan MD, MPH - Reproductive Genetics

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This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.