Stool DNA Test

The stool DNA test, also known as the stool DNA screening test or Cologuard, is a non-invasive diagnostic tool used to detect colon cancer and precancerous polyps in the colon.

How it Works

The test analyzes a stool sample for abnormal DNA from colon cancer cells or precancerous polyps. The test looks for specific genetic mutations that are commonly found in colon cancer and precancerous polyps, as well as blood in the stool, which can be a sign of colon cancer.

What the Test Detects

The stool DNA test detects:

• Abnormal DNA from colon cancer cells or precancerous polyps
• Blood in the stool (hemoglobin)
• Methylated genes, which are genes that have been altered by the addition of a methyl group, a common feature of colon cancer cells

How to Prepare for the Test

To prepare for the test, patients typically:

• Avoid certain medications, such as aspirin and ibuprofen, that can interfere with the test results
• Avoid eating certain foods, such as red meat, that can affect the test results
• Collect a stool sample using a special kit provided by the doctor or laboratory

Interpreting Test Results

The test results are typically reported as:

• Positive: abnormal DNA or blood is detected in the stool, which may indicate colon cancer or precancerous polyps
• Negative: no abnormal DNA or blood is detected in the stool, which suggests that colon cancer or precancerous polyps are unlikely
• Uncertain or inconclusive: the test results are unclear or cannot be interpreted

Limitations and Risks

The stool DNA test has several limitations and risks, including:

• False positive results: the test may detect abnormal DNA or blood in the stool when no colon cancer or precancerous polyps are present
• False negative results: the test may fail to detect colon cancer or precancerous polyps when they are present
• The test does not detect all types of colon cancer, such as serrated polyps

Recommendations and Guidelines

The American Cancer Society recommends that adults aged 45 to 75 years undergo regular screening for colon cancer using one of several tests, including the stool DNA test. The US Preventive Services Task Force also recommends screening for colon cancer in adults aged 50 to 75 years.