Screening Tests: Purpose & Types

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Screening tests are important for catching diseases early or preventing them altogether. In this lesson we'll talk about screening tests that help keep you healthy from the time before you are born all the way through adulthood.

What are Screening Tests?

When you don't feel well you visit your doctor to get checked out. The doctor might take your temperature, draw some blood, and perform other diagnostic tests. These are helpful tests to figure out why you aren't feeling well and treat whatever is causing you to be sick.

But sometimes a doctor will perform tests when you have no symptoms at all. These are called screening tests and they test whether you have or are at risk for diseases or disorders in early stages, when they may not yet be causing symptoms. Screening tests are important because they can detect problems early, when they are easier to treat. These tests can also help detect changes in your body over time when you have them done routinely.

Many different screening tests can be performed. Some depend on your age, your gender, your lifestyle choices (such as diet and exercise), your family history, your heritage, where you have lived in the world, and more. Let's take a closer look at some important screening tests and see how they can help in the early detection of disease.

Antenatal Screening Tests

Believe it or not, you can have screening tests done before you are even born! These are called antenatal tests because they are done before birth. Amniocentesis samples the amniotic fluid around the fetus with a needle. This screen tests for chromosomal abnormalities, such as Down syndrome, neural tube defects such as spina bifida, and genetic disorders such as cystic fibrosis. Amniocentesis is a very good screening test because it can indicate with a high level of certainty if these defects are present, but it can't tell you to what degree. Other advanced level testing may be needed to gather more information.

Down syndrome can be screened for during pregnancy with various antenatal tests.
down syndrome

Chorionic villus sampling or CVS is another antenatal screening test that can be used to test for chromosomal and genetic defects, as well as sex-linked disorders such as muscular dystrophy. Chorionic villi are projections off the placenta that are important during pregnancy because they provide maximum contact with the mother's blood. A sample of chorionic villi is taken through the abdomen with a needle or through the vagina with a tube that reaches up to the placenta.

During your pregnancy your doctor may also order blood tests to ensure there are no other potential complications. Like most other blood tests, this will involve a small sample drawn from your arm. It will be analyzed for different things, such as anemia, a condition where there are too few red blood cells, or the Rh factor, a type of protein on the surface of red blood cells. This is important to test for because if the mother is Rh-negative (she does not have the protein) and the baby is Rh-positive (it does have the protein) then the mother's blood may attack the baby's blood.

Infant & Child Screening Tests

Don't worry, there are plenty of screening tests that can be done after you are born. One that is required for all newborns in the U.S. is a blood test for phenylketonuria or PKU. This is an amino acid disorder that makes it difficult to break down phenylalanine (an amino acid) in the food we eat. This test is very important; if left untreated, babies with PKU may have developmental and intellectual disabilities later in life.

As you get older and your teeth come in, you'll want to have regular dental examinations to monitor caries or tooth decay. Tooth decay can often be prevented. If it is present and left untreated, it can lead to pain, holes in your teeth, and even tooth loss. It's never too early to get dental checkups!

Another important screening test for young children checks for visual problems using a Snellen chart. This is that chart with the large 'E' at the top, with rows of letters that get progressively smaller moving down the chart. For this test, each eye should be tested individually. The results provide a baseline for your vision and help determine if there are visual problems in either eye.

The Snellen eye-test chart helps screen for vision deficits and difficulties.
snellen eye test chart

Hearing tests are also important screening tests for young children. To test your hearing you will be put in a soundproof room that excludes external noise. An audiologist will play sounds and you will be asked to push a button that signals when you have heard the noise. Results are plotted on an audiogram, which is a chart that compares what you actually heard to what you should have heard.

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