Stool DNA Test

Home / Stool DNA Test

[lwptoc] Overview  The stool DNA test, also known as Cologuard, is a newly developed non-invasive rapid test to screen for colon cancer. Its mode of action is to identify DNA changes in the cells of stool samples or identify abnormal DNA linked with colon cancer. To ensure a high detection rate and counter the differing… Read More

Stool DNA Test



The stool DNA test, also known as Cologuard, is a newly developed non-invasive rapid test to screen for colon cancer. Its mode of action is to identify DNA changes in the cells of stool samples or identify abnormal DNA linked with colon cancer. To ensure a high detection rate and counter the differing DNA changes and mutations, the test kit is designed to target multiple DNA markers.

It also fortified to detect hidden blood in stool samples. If it, however, gives a positive result, additional testing may be required to ensure a proper diagnosis. 

The invention of the stool DNA test makes it easy for screening for colon cancer, as it can be self-done and even carried out in the privacy of your home.

Why it may be required?

A stool DNA test may be required to screen for colon cancer or precancerous polyps in asymptomatic people. It is usually used to diagnose colon cancer in those aged 50 and above.

Test sample and procedure.

The sample required for the test procedure is stool. 

When cancer or polyps is present in the colon, it continuously shed cells with abnormal DNA changes into the stool. The DNA changes are usually present in tiny amounts. Thus, requiring very sensitive laboratory methods to detect them.  The stool DNA test detects these abnormal DNA changes and the tiny amounts of blood that may have been shed into the stool from the digestive tract due to colon cancer. 

  • Abnormal DNA change: Cancer is usually caused by DNA changes inside our cells, and these changes can cause the cells to grow rapidly and divide uncontrollably. The stool DNA test is designed to detect the DNA changes in our cells that are caused by the presence of colon cancer.
  • Hidden blood: The stool DNA test makes use of a method called fecal immunochemical testing to detect occult blood (that is, trace amounts of blood) in the stool. The fecal immunochemical test spots the globin (that is, protein) part of hemoglobin in red blood cells. The test is actually specifically designed to detect the globin from human blood and not the ones from the foods that we consume (for example; fish and meat). Therefore, dietary restrictions are not required before doing the test. 

However, it should be noted that the test is not for everyone and it’s not a replacement for colonoscopy if you have had an abnormal colonoscopy in the past or have a family history of colon cancer. In fact, a positive stool DNA test result requires a colonoscopy, to examine the inside of your colon for polyps and cancer. 

Potential risk

There is no risk, whatsoever, associated with this testing method.

What do you need to prepare before taking the test?

There is no formal preparation required for it. No precautions also must be observed. You are free to eat, drink and use the toilet before taking your stool DNA test. For those that have diarrhea, it is best to let the diarrhea be resolve before taking the test. However, it is best you have a discussion with your doctor first before taking the test.

What you should likely expect before taking the test?

If you are to undergo a stool DNA test, you will be required to collect a stool sample and submit it to your doctor’s office or mail it to a designated laboratory.

You will be given a stool DNA test kit for collection and submission of the stool sample. The kit includes a container and a preservative solution. The stool sample is collected into the container. The preservative solution is added to the stool sample before sealing the container. After the collection of the stool sample, you will take it to the doctor’s office or laboratory for analysis. The stool DNA test procedures require only a stool sample. However, your doctor may ask for another product if need be.

Interpretation of your result. 

For simplicity of understanding, I’ve decided to split the stool DNA test result interpretation into stool DNA and Stool immunochemical test

Stool DNA

The could be either positive or negative

Negative result: this means that the DNA changes associated with colon cancer have not been detected. So, you probably don’t have colon cancer as at the time the test was conducted.

Positive result: this means that abnormal DNA changes are found and there are likely chances of cancer presence. However, an advanced test is usually recommended for proper diagnosis and certainty.

Stool immunochemical test

This could also be either a positive or negative result 

Negative result: in other words, what this means is no hemoglobin was detected in the stool sample as at the time it was tested.

Positive result: this is an indication of abnormal bleeding in the lower digestive tract. However, while this bleeding could be caused by colon cancer, it is also possible that it is caused by ulcers, polyps, or hemorrhoids

It should, however, be noted that when a stool DNA test, either the stool DNA or stool immunochemical test, is negative, it is best that the screening is repeated at intervals, usually every three (3) years. 

As for a positive result, either the stool DNA or stool immunochemical test requires follow-up testing, and a colonoscopy is best recommended. This allows the doctor to examine the internal part of the colon to see if cancer or polyps are present, and subsequently remove them.

Statistics has it that every 20 people who carry out a stool DNA test, one or two will have a positive result, but upon a follow-up colonoscopy no cancer or polyps will be found. In instances like this, further testing is usually not recommended. 

Benefits and disadvantages of a stool DNA test.

The stool DNA test has some advantages over another screening test for colon cancer. Some of which include,

  • The test can be shipped directly to and from the patient’s home.
  • The test can be completed in the privacy and comfort of your own home.
  • It requires no preparation, no dietary restrictions, or any alteration or changes to medications necessary.

However, the disadvantage is it requires a follow-up colonoscopy when abnormalities are detected. In other words, it cannot be used as a final decisive diagnosis.

Conclusively, while this newly developed technique has proven to be a critical step in beating this common and preventable cancer by making it easy for more people to get screened and earlier, it is important to talk to your doctor about the best option for you.