While a blood test for colon cancer screening may sound convenient, the American Society for Gastrointestinal Endoscopy (ASGE) issued a formal statement in August 2025 advising patients on why these tests are not a replacement for traditional screening.
What You Need to Know
- Not a First Choice: The ASGE recommends that blood-based tests should not be used as your primary screening method. They should only be considered if you have already refused a colonoscopy and stool-based tests (like FIT or Cologuard).
- The “Pre-Cancer” Gap: The biggest drawback of the blood test is its low ability to find precancerous polyps. It only catches about 13% of these growths, whereas a colonoscopy finds nearly all of them. Finding and removing polyps is the only way to prevent cancer before it starts.
- If the Test is Positive: If you choose a blood test and it returns a positive result, you must have a colonoscopy to find the cause.
- Higher Risk: Studies show that relying solely on blood tests instead of colonoscopies could actually lead to an increase in cancer cases and deaths because too many early-stage issues are missed.
Why Colonoscopy Remains the “Gold Standard”
Colonoscopy remains the most effective tool because it allows your doctor to see, find, and remove polyps during the same procedure. This prevents cancer from ever developing.
| Screening Method | Finds Precancerous Polyps? | Finds Early Stage Cancer? |
| Colonoscopy | 92% – 95% (Excellent) | 96% (Excellent) |
| Stool Tests (FIT/sDNA) | 42% (Fair) | 92% (Good) |
| Blood Test (Shield) | 13% (Poor) | 83% (Moderate) |
Our Recommendation
We follow the ASGE guidelines and recommend Colonoscopy as the preferred screening method for most patients starting at age 45.
If you are hesitant about a colonoscopy, please call us to discuss which screening option is safest for your specific health history.