Doctors check poop for DNA as part of the screening process for colorectal cancer. It helps doctors diagnose people with this disease during its early stages or even when the cells are precancerous.
Changes, or mutations, in DNA can be markers for cancer. According to the
Each DNA molecule consists of two strands that twist around each other, making a shape called a double helix. Although some DNA is unique to each individual, most DNA follows patterns.
Scientists know that the nitrogen bases pair up in recognizable patterns or
Tiny changes in a cell’s DNA can make it cancerous. Different types of cancer change the DNA in different ways, but they also follow a pattern. Changes, or mutations, in the DNA sequence alert doctors to cancerous cells.
Human poop is mostly water and the remains of food after digestion. It also contains some cells from the digestive tract, and these cells contain DNA.
Sometimes poop contains microscopic amounts of blood. Blood cells also contain DNA. The
Where else can DNA appear in the human body?
Almost every cell in a person’s body contains DNA.
DNA can appear in:
- skin cells
- blood cells
For the test, people collect their entire stool and send it to a laboratory for analysis.
Individuals receive a special kit to collect the sample, usually through the mail. The kit consists of a sample container, preservative liquid, a bracket for holding the collection container in the toilet, a tube, labels, a shipping box, and instructions.
After collecting the sample, a person mails it to a laboratory. For the test to work, the sample has to reach the laboratory within 72 hours, and people should mail the sample within 24 hours of taking it.
- High-sensitivity guaiac-based fecal occult blood test: Every year
- FIT: Every year
- sDNA-FIT: Every 1–3 years
- Colonoscopy: Every 10 years
- CT colonography Every 5 years
- Fecal sigmoidoscopy: Every 5 years
- Fecal sigmoidoscopy with FIT: Fecal sigmoidoscopy every 10 years plus FIT every year
Doctors test feces for DNA to check for any mutations in the DNA sequencing. Mutations may indicate that cells are cancerous or precancerous.
These tests can reveal cancerous cells before a person experiences any symptoms.
According to the
Treating cancers early, either before cells become cancerous or before the disease has spread, increases the likelihood of a person surviving. The ACS estimates that over
Testing stool for DNA is noninvasive, meaning it does not require a medical procedure. People can collect their samples in the privacy of their own homes.
In 2014, the Food and Drug Administration (FDA) approved Cologuard as the first DNA-based stool testing kit, according to the Colorectal Cancer Alliance.
Most health insurers in the United States completely cover the cost of the tests. Even the postage to the laboratory is prepaid.
People taking Cologuard tests do not need to change their eating or drinking habits before the test.
Cologuard tests check for DNA and blood in a person’s feces. Information from the test’s information leaflet describes the results as positive, negative, or no result obtained.
If the DNA shows signs of mutations that could lead to colorectal cancer, the test result is positive.
Doctors advise people with a positive result to have a
If the polyps are cancerous, doctors can remove them before the cancer spreads to other parts of the body.
A negative result means the person’s feces do not contain DNA or blood.
If there is no result, it means the test was not conclusive. People with this result may need to provide another stool sample for testing.
Although the testing is usually accurate, it is possible to have a false-positive or false-negative result. In these rare cases, the results may indicate that a person has precancerous cells when they do not or that it did not detect atypical DNA when it was actually present in the body.
Testing poop for DNA is a noninvasive test that people can do once every
Poop contains DNA, which doctors can analyze and find abnormalities, or mutations, that might lead to cancer.
Colorectal cancers are cancers of the colon and rectum. The DNA from feces can reveal the presence of precancerous or cancerous cells before a person experiences any symptoms.
Doctors can remove any polyps or growths from someone’s intestines before cancer spreads to other parts of the body.
Health insurers in the U.S. usually cover the cost of a stool DNA test once every 3 years.