Considerations: Colonoscopy or Cologuard®

Cologuard is a stool-based colo-rectal cancer screening test that accurately identifies 92 out of 100 cancers, and 42 out of 100 precancerous polyps.

Colonoscopy is a cancer detection and cancer prevention procedure that is more accurate at identifying cancers than Cologuard because the patient’s colon is visually inspected with an endoscope. Colonoscopy prevents colon cancer because the gastroenterologist removes precancerous polyps found during the screening examination. Precancerous polyps are found in 20% of women and 30% of men age 50 and older.

Cologuard may produce false positive results in 10%-13% of patients—stool positive, but nothing found on later colonoscopy. Patients with a positive Cologuard finding will require subsequent colonoscopy.

Both Cologuard and colonoscopy are covered by commercial insurance and Medicare as a one-time screening benefit with little to no out-of-pocket cost to the patient. The list price of Cologuard is $650 (Medicare $500). The cost of colonoscopy performed in a community-based ambulatory surgery center is approximately $700 to $1,300 (Medicare $650).

Cologuard is more convenient because the stool specimen can be obtained by the patient.

Advances in colonoscopy including lower volume preparations, Propofol anesthesia, and carbon dioxide for insufflation of the colon, have made colonoscopy safe with faster recovery times and less patient discomfort.


Cologuard is not recommended for patients with a family history of colon cancer, polyps, or genetic polyp syndromes; or patients with Ulcerative colitis, Crohn’s disease, or patients with symptoms including blood in the stool, rectal bleeding, diarrhea, or abdominal pain.


Why is Colon cancer screening important?

Colo-rectal cancer (CRC) remains the second most common cancer caused death in the U.S. for both men and women. One in 17 Americans, (over 50,000 for 2018) will develop CRC death in their lifetime. The good news is there has been a 46% decrease in CRC death since its peak in 1985. Due to CRC screening methods, new colon cancer cases have come down from 66 per 100,000 population in 1985 to 37 cases in 2015.


Despite evidence that early screening prevents CRC, approximately 30% of appropriate individuals are not screened. Current guidelines recommend the initiation of CRC screening for average-risk individuals at age 50 (45 for African Americans). Risks increase sharply after age 50. Recent studies may be showing that screening at younger ages may be prudent.


In the past tests recommended by national prevention organizations included: colonoscopy, flexible sigmoidoscopy and fecal occult blood testing.

What is the difference between screening for colon cancer and polyps?

It is important to distinguish screening detection for cancer and earlier pre-cancerous advanced adenomas (AA) in evaluating screening techniques. AA can be removed early on, during colonoscopy to prevent CRC development.

What are options for colon cancer screening?

Stool testing for CRC screening remains a popular concept for many individuals, as it is relative quick, easy and non-invasive. Stool testing includes Fecal Occult blood test (FOBT), Fecal immune chemical test (FIT), and the new technology of Multi-targeted stool DNA test (MT-sDNA)

What is Cologuard®?

Multi-targeted stool DNA test (MT-sDNA) Cologuard
Cologuard is a propriety name for the first and presently only commercially available MT-sDNA. This is a new method of stool testing based on the detection of DNA continuously shed from neoplastic (polyps and cancer) cells into the colon canal. This DNA is stable and can be amplified in the lab. The lab detects highly discriminant markers DNA, which represent molecular pathways used by abnormal but not normal colon cells.


The test checks for 11 markers: BMP3, NDRG4, k-ras oncogenes (the 7 most informative point DNA mutations), beta-actin (a marker for total human DNA), and fecal hemoglobin. Because of the check for fecal hemoglobin this test should not be done in individuals actively bleeding or experiencing diarrhea. To be accurate stool samples must promptly arrive at the laboratory within 72 hours of being obtained.

How does Cologuard compare to Colonoscopy?

Compared to the Gold standard of colonoscopy studies have shown a single Cologuard stool testing accurately identified 92 of every 100 colon cancers but missing 8 colon cancers. This was better than stool FIT which only picked up 73 of 100. The detection of pre-cancerous polyps (Advanced adenomas) was lower finding only 42 of 100, missing 58, better than FIT, which only detected 23 of 100.


All positive tests should be followed by colonoscopy for evaluation of all lesions of the colon.


“Cologuard” may produce false positive results: stool positive but nothing found on later colonoscopy. This was in 10-13% of the study trial and was higher than the more reasonably priced FIT (only 3-5%). Studies show false positives are higher in individual over 65 than those age 50.


“Cologuard” may also produce false negative result: stool negative but eventual colonoscopy finds cancer or advanced adenoma.


Studies do show good patient acceptance and compliance of this screening method, with two thirds of patients completing testing within 60 days of testing kits sent home. However, one third of patients did not complete this otherwise easy test. In a study of Medicare age patients 88% of patients completed testing when failing to complete previous referral for CRC screening.

What is the long-term follow up on Cologuard use?

A onetime negative “Cologuard” does not guarantee absence of cancer or advanced adenomas and individuals should have ongoing follow up screening. Repeat screening interval and use of “Cologuard” has not been established or studied. However on that basis of mathematical modeling The Center for Medicare & Medicaid Services (CMS), American Cancer Society and National Comprehensive Cancer Network have approved Cologuard for testing every 3 years.

How much will Cologuard Cost Me?

While the test is a covered preventive screening benefit by most health insurers without charges, any subsequent colonoscopy for positive test results would fall under symptomatic colonoscopy requiring copay and deductible medical expenses.

How much will Cologuard cost U.S. medical care?

There has been no cost effectiveness data on “Cologuard” as a long term screening method to prevent CRC or to catch cancer at earlier stage. Out-of pocket list price is approximately $650 (Medicare cost $500). Modeling costs for every 3 years Cologuard sums to $216 each year compared to not screening $11,313 annual costs.

What is overall benefit?

Emerging studies show that Multi-targeted stool DNA testing with ColoGuard (in concert with colonoscopy for positive tests) does provide an easy acceptable CRC screening option for those unwilling to have colonoscopy. It has some significant drawbacks in terms of missing significant lesions, and falsely positive results that may lead to extra colonoscopy.

Who may be appropriate for Cologuard?

Asymptomatic screening age 50 and over at average risk

Who should NOT utilize Cologuard?
  • Patients with a history of colon cancer
  • Patients with history of polyps
  • Patients with family history of colon cancer
  • Patients with a history of genetic polyp syndromes
  • Patients with Ulcerative colitis or Crohn’s disease
  • Patients with any symptoms including blood in stool, rectal bleeding, diarrhea, or abdominal pain


Imperiale, T.F. et al New England Journal of Medicine. 2014 .370(14):1289-1297.

Redwood DG et al Mayo Clinic Proceedings 2016 (91): 61-70.

Itzkowitz SH Practical Gastro July 2016 : 26-35