From Jayadev Mettu, MD, medical oncologist and hematologist at OHC

March 27, 2023

Colonoscopy. The word typically conjures up unpleasant thoughts of bowel prep, a liquid diet, and embarrassment. It’s no wonder that at-home colon cancer screening tests offer greater appeal. Before you cancel your colonoscopy to run out and purchase an at-home testing kit, arm yourself with all you need to know about colon cancer screening.

Typically, colon cancer is slow-growing and in its early stages, it can be asymptomatic. Screening can prevent disease development and detect colon cancer early when treatments are typically more effective. The U.S. Multi-Society Task Force on Colorectal Cancer (USMSTF) has approved six methods for colorectal cancer screening:

  • Colonoscopy
  • CT (computed tomography) colonography, or virtual colonoscopy
  • Flexible sigmoidoscopy
  • Capsule endoscopy
  • Fecal immunochemistry test (FIT or iFOBT)
  • FIT-fecal DNA

The last two methods are fecal occult blood tests (FOBT) that do not require bowel preparation to clear the bowel for visualization. Let’s take a closer look at FOBTs and better understand why they have been gaining in popularity.

FOBTs are FDA-approved colon cancer screening options for those at average risk of colon cancer who do not have any symptoms of the disease available for purchase without a prescription. The tests, which can be performed at home, look for the microscopic presence of blood in a stool sample. In addition to the FOBTs mentioned above, there is a third option, the guaiac FOBT (gFOBT), which is less popular because of its cost and decreased sensitivity.

To use the FIT, an individual inserts a portion of a stool sample into a sampling bottle or tube and sends it to a lab for evaluation. Testing uses antibodies that bind to hemoglobin protein indicating whether blood is in the stool. This test should be done annually.

The FIT DNA test, or stool DNA test, combines the FIT with an additional search for altered DNA in the stool sample. Cologuard is one example. After collecting the sample and sending it to a lab, the lab will extract DNA from the stool to identify the presence and scope of any abnormal genes. This test should be done every three years.

Preparation for FOBTs typically involves avoiding certain fruits and vegetables, red meat, Vitamin C supplements, and pain relievers for a few days.

A positive result from a FOBT indicates there is blood in the stool but does not confirm a cancer diagnosis. Blood in stool means there is bleeding in the digestive tract, which can be caused by a variety of conditions including anemia, inflammatory bowel disease, ulcers, hemorrhoids, and benign tumors.

These at-home stool screening tests do have some limitations. If blood is detected, additional tests like a colonoscopy will need to be done. FOBTs are not as accurate as other methods of colon cancer screening. There is a risk for either a false-positive or false-negative result, and some tests reveal an inconclusive result that indicates there may have been an issue with specimen collection.

The colonoscopy remains the gold standard of colon cancer screening and can prevent colon cancer through the detection and removal of polyps, non-cancerous growths in the lining of the bowel that can become cancerous. Recent years have brought us smaller-volume colonoscopy preps that taste better. Also, there is an FDA-approved bowel prep tablet option. Most patients are sedated during the 30-minute procedure and do not feel anything during the exam or remember anything from the test. Recovery only takes about an hour. Moreover, a colonoscopy is better than becoming a statistic. The American Cancer Society estimates that there will be 46,050 new cases of colon cancer in the U.S. this year.

Stay up to date on the latest colon cancer screening guidelines, which can be found here. Recently, screening guidelines were adjusted to bring the initial screening age for average risk individuals down to 45 from 50 because of the increasing incidence of colon cancer in younger adults. Recommendations vary based on age and risk, so discuss your screening schedule with your healthcare provider.

While FOBTs are an appealing option for colon cancer screening, they do have some drawbacks and are not as reliable as the colonoscopy. Still, some form of screening is better than none. Like most cancers, early detection of colon cancer typically results in better outcomes. For more information on cancer prevention or screening or to request a second opinion with an OHC cancer expert, call 1-888-649-4800 or visit

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