No Blood Work Required for Cologuard Screening
Cologuard is a stool-based DNA test that does not require any blood work—it is performed entirely on a stool sample collected at home. 1
What Cologuard Actually Tests
Cologuard is a multitarget stool DNA (mt-sDNA) test that combines detection of DNA alterations with an immunochemical test for occult blood, all performed on a single stool specimen. 2
The test analyzes stool for abnormal DNA markers and hemoglobin (blood) that may indicate colorectal cancer or precancerous lesions—no blood draw or blood work is involved in the testing process. 3, 4
Patients collect the stool sample at home using a provided kit and mail it to the laboratory for analysis. 5
Guideline-Endorsed Screening Options
The American Cancer Society and U.S. Multi-Society Task Force endorse Cologuard as an acceptable screening option for average-risk adults aged 45-85 years, to be performed every 3 years. 1, 6
Available colorectal cancer screening options include: 1
Stool-based tests (no blood work):
- Fecal immunochemical test (FIT) annually
- High-sensitivity guaiac-based fecal occult blood test annually
- Multitarget stool DNA test (Cologuard) every 3 years
Structural examinations (no blood work):
- Colonoscopy every 10 years
- CT colonography every 5 years
- Flexible sigmoidoscopy every 5 years
Important Follow-Up Requirements
Any positive Cologuard result requires prompt diagnostic colonoscopy—this is the only follow-up needed, not additional blood work. 1, 6
Cologuard has a specificity of 86.6-87%, meaning approximately 13-14% of people without colorectal cancer will have a false positive result. 7
When Cologuard is positive but follow-up colonoscopy is negative, no further evaluation (including blood work or upper endoscopy) is indicated in asymptomatic patients. 7
Common Pitfall to Avoid
Do not order blood-based circulating tumor DNA tests (such as Shield) for colorectal cancer screening, as these are not endorsed by any major guideline and remain investigational. 6 Blood-based tests are explicitly excluded from USPSTF recommendations due to limited evidence, and they should not be presented as equivalent to guideline-endorsed options like Cologuard. 6