While we can agree that colon cancer screening is a vital part of health maintenance, deciding which colon cancer screening test to choose can feel overwhelming. Which option is right for you? Well, as with anything else, knowledge is power. The more you know about these two different, yet essential methods of colon cancer screening, the easier it is to make an informed decision on which is better for you.

We’re going to discuss the differences between a colonoscopy and the Cologuard test. But first, let’s talk about why colon cancer screening is vitally important.

Why Is Colon Cancer Screening so Important?

Did you know that 1 out of every 20 people will be affected by colon cancer? This cancer is very treatable when detected at an early stage. So, when do you need to start being screened for colon cancer? The American Cancer Society recommends that persons at average risk should begin regular colon cancer screening once they turn 45 years old. Patients with no family history of colon cancer and no gut-related symptoms are considered average risk. Colonoscopy or a stool-based test like the Cologuard can be used to screen for colon cancer.

The screening guidelines for the detection of colon cancer are as follows:

  • Regular colon cancer screening until at 75
  • At age 75, the decision to continue routine screening is based on life expectancy, preferences, screening history, and overall health. In short, clinicians will weigh the risks of a repeat procedure against the potential benefits to the patient
  • After 85 years of age, colorectal cancer screenings are not typically done.

While the above is true for patients at average risk of colon cancer, patients that are at an increased risk of colorectal cancer will start screening before age 45. These patients may need more specific testing and will need to be tested more often (than patients at average risk). You’re considered at an increased risk of colorectal cancer if you meet the following criteria:

  • Family history of colon cancer or polyps
  • Personal history of polyps or colon cancer
  • History of Crohn’s disease or ulcerative colitis
  • History of abdominal radiation
  • Specific genetic syndromes or ethnicity (African American)

Colon Polyps Overview

A colon polyp is a piece of tissue that protrudes from the inside of the large intestine or colon. While most polyps are harmless, some can become cancer if given enough time and neglect. Small polyps often cause no symptoms at all. Still, if polyps become large enough, you may experience blood in your stool or on your toilet paper after a bowel movement. Other symptoms of enlarging polyps include a change in your bowel habits (for instance, persistent diarrhea or new constipation).

You’re more likely to develop polyps if:

  • You have a personal history of colon polyps
  • You are over age 50
  • You have a family history of colon cancer
  • You have a family history of polyps

Colon polyps can be easily removed during a colonoscopy. Then they are checked to see if they’re cancerous or pre-cancerous.


A colonoscopy is considered the “gold standard” exam for colon cancer screening. It’s thorough and comprehensive nature allows the exam to detect even the small abnormalities inside of your colon. These abnormalities cannot be identified by stool-based colon cancer tests. If a polyp is detected during a colonoscopy, that polyp can be removed on the spot, and you do not have to undergo a second procedure to remove the polyp then.

How does colonoscopy work? Your healthcare provider will give you instructions to follow to clear out your colon (of all stool) before the procedure. This generally involves staying on a clear liquid diet for 24-hours before the colonoscopy and then consuming a liquid prep the evening before your colonoscopy.

During a colonoscopy, your doctor inserts an instrument called a scope inside of your large intestine through your rectum. The scope includes a tiny camera attached to a long tube that allows a clear view of irregularities such as polyps, inflammation, ulcers, or any other abnormal growths. If any polyps or irregularities are detected, they can be removed and or a biopsy is done for further testing. Patients are made comfortable with a sedative that allows them to sleep right through the procedure.

Types of Colonoscopies

Generally, there are two different types of colonoscopies – screening and diagnostic. A screening colonoscopy is preventative. This means that the patient isn’t having any symptoms of colon cancer, has no known family or personal history of colon cancer, and just needs a routine screening exam.

A diagnostic colonoscopy is different because it’s done when a patient does have colon cancer symptoms. These could include blood in the stool, new abdominal pain, or change in bowel habits, to name a few. Other factors indicating a diagnostic colonoscopy are that a patient has a personal history of colon polyps, or has a family or personal history of colon cancer. Your doctor will use a diagnostic exam to diagnose what is going on inside of the colon. As an example, rectal bleeding is a common symptom that could require a diagnostic colonoscopy to determine the cause of bleeding.

NOTE: Cologuard is only used for average-risk screening and not diagnostic exams. The reason is that Cologuard tests your stool for altered DNA or blood but cannot make a definitive diagnosis on its own. Therefore, a positive Cologuard test requires a follow-up diagnostic colonoscopy.

Another important distinction is that most insurance policies do not fully cover the costs of a diagnostic colonoscopy. When scheduling your colonoscopy, patients should state whether this is a routine screening or needed due to symptoms/illness. Patients need to discuss all costs with their insurance provider before their colonoscopy to eliminate the possibility of unexpected expenses.

Colonoscopy Pros and Cons

There are some pros and cons to be aware of before you undergo a colonoscopy.

The pros of having a colonoscopy include:

  • It’s the most complete exam for detection and removal of all cancerous and precancerous polyps
  • It allows complete visualization of your colon
  • Required every 10 years instead of every 3 years required with the Cologuard test. An important distinction is that your provider will recommend a colonoscopy more frequently than every 10 years if you have colon polyps
  • It’s the only acceptable test for symptomatic patients
  • Abnormal growths such as polyps can be removed on the spot, at the time of your colonoscopy

The cons of having a colonoscopy include:

  • Invasive
  • Requires bowel preparation prior to the procedure
  • Sedated procedure – plan to have someone drive you home
  • Small risk of complication (1 in 1750 colonoscopies)
  • Bleeding at the site of polyp removal, anesthesia complications or can cause a small tear in the colon
  • Possible short period of cramping or bloating


Cologuard is an at-home, do it yourself stool collection exam. It allows you to mail in your specimen to a laboratory from the privacy of your own home. Cologuard examines your stool for two things: 1) blood from the colon and 2) altered DNA that may be pre-cancerous or cancerous. This modified DNA comes from cells that have been shed into your stool, as DNA is continuously shed from your intestinal linings’ cells.

Once you send in your stool sample to a laboratory, your doctor gets the results in just two weeks. If abnormalities are found, your healthcare provider will devise a plan of action that will more than likely require a follow-up colonoscopy to determine why you had a positive Cologuard.

Cologuard is designed for people such as:

  • Those 45 years or older
  • Average risk of colon cancer
  • No family history or personal history of colon cancer
  • No personal or family history of polyps

Cologuard isn’t for everyone and isn’t a replacement for a colonoscopy. What it does is helps identify at-risk individuals to get them further evaluated via a diagnostic exam like a colonoscopy. It has gained popularity because it’s convenient, requires no preparation, and can be done in the privacy of your own home.

Cologuard Pros and Cons

There are some pros and cons to be aware of before you undergo the Cologuard test.

The pros of Cologuard include:

  • Non-invasive
  • No bowel preparation
  • Convenient
  • Private
  • No risk of complications from the exam

The cons of Cologuard include:

  • Required every three years
  • 13% false-positive rate (test returns are positive, however no abnormalities are found during a colonoscopy)
  • Misses 8% of colorectal cancers
  • Misses 60% of advanced polyps are those that are larger than 10-mm or ones that can behave in a more aggressive growth manner than other colon polyps)
  • If the Cologuard test is positive, the patient will need to schedule a colonoscopy. Unfortunately, this isn’t fully covered by insurance since it will be a diagnostic exam, not a screening exam.
  • Since Cologuard is relatively new, there is no long-term data

Understanding the Differences Between a Colonoscopy and Cologuard

Now that you have a clear picture of what a colonoscopy and the Cologuard test entail let’s review some key differences between the two exams.

Invasive vs Non-InvasiveInvasiveNon-invasive
PreparationColon cleansing required, along with fasting, prior to the procedure.No preparation needed.
Polyp DetectionPolyps can be found and removed during the exam.Indirectly tests for the symptoms of colon cancer and polyps – blood and altered DNA in the stool.
AccuracyMost accurate of all colon cancer screenings. In one study a colonoscopy diagnosed 65 cancers while the Cologuard found only 92% of the 65 cancers (the Cologuard missed 5 cancers in this study). Also, a colonoscopy found 757 precancerous polyps with the Cologuard only finding 42% of the 757 (Cologuard missed the diagnosis of 440 polyps).Found 92% of colon cancers and 42% of high-risk precancers in the same study making it less reliable than a colonoscopy.
FrequencyEvery ten years — as long as no abnormalities are found.Every three years — as long as the Cologuard is a negative test

Insured and Non-insured

Insured and Non-Insured Insured: Your deductible amount – typically $0 – $1000+

Non-insured: $2,000 to $3,764

Insured: May be covered by insurance depending on your plan and benefits.

Non-insured: $649

Which Colon Cancer Test is the Best?

As a physician, I fully support all efforts to bring awareness to and screen for colon cancer. Millions of Americans over 45 years of age not being tested each year. It’s a focus of my gastroenterology practice to do what we can to help these adults in the Bedford and the surrounding Fort Worth areas not to become a statistic since this is a preventable cancer.

That being said, I do recommend colonoscopy over Cologuard and other tests. My recommendation is due to the accuracy and unique ability that allows your doctor to view the colon and biopsy/remove any polyps. My primary goal is to increase the number of adults getting screened. If you do not feel that colonoscopy is your best option, please consult with your doctor regarding other testing options like Cologuard.

If you live in the Bedford, TX area and are looking for a gastroenterologist for a colonoscopy, you can use my website to schedule an appointment or by calling us at 817-267-8470.

If you would like to bypass an office visit prior to your screening colonoscopy, inquire with my scheduler about the Open Colonoscopy option. It will save qualifying patients the time and expense of an office visit prior to their colonoscopy.

-Thomas Lyles, MD