Should You Repeat an Abnormal Cologuard Test?
No, you should never repeat an abnormal Cologuard test—proceed directly to diagnostic colonoscopy. Repeating stool-based tests after a positive result is a common clinical error that delays diagnosis and does not conform to established guidelines 1, 2.
Why Colonoscopy is Mandatory
Any positive stool DNA test (including Cologuard) requires follow-up colonoscopy as the sole appropriate next step. 1, 2
- There is no justification for repeating FOBT or stool DNA tests in response to an initial positive finding 1
- Colonoscopy is substantially more accurate than alternative methods for detecting both cancers and adenomas 2
- The diagnostic yield is significant: approximately 10% probability of cancer and 37% probability of polyps in patients with positive stool-based tests 2, 3
Timing of Follow-Up Colonoscopy
Target completion of diagnostic colonoscopy within 60 days of the positive Cologuard result. 1, 3
- Earlier diagnostic testing decreases the risk of progression from preneoplastic disease to cancer and from early-stage to late-stage cancers 1
- Longer waiting times between positive screening and diagnostic evaluation increase the risk that patients may change contact information, insurance coverage, or providers, complicating follow-up 1
- Studies show that the probability of diagnostic colonoscopy after a positive fecal test plateaus at approximately 80% after 6 months, even in highly organized systems 1
What NOT to Do
Avoid these common pitfalls that delay appropriate care:
- Do not use flexible sigmoidoscopy alone—it is inadequate because colonoscopy examines the entire colon and can simultaneously remove significant neoplasia 2
- Do not substitute barium enema—colonoscopy remains the gold standard for complete evaluation 2
- Do not use CT colonography as initial follow-up—direct colonoscopy is indicated for positive screening tests 2
- Do not collect a single stool sample on the clinician's fingertip during digital rectal examination—this is not recommended 1
Expected Findings on Colonoscopy
Patients with positive Cologuard tests have substantial rates of clinically significant pathology:
- In patients with a previously negative colonoscopy and subsequent positive Cologuard, 30% had advanced adenomas on follow-up colonoscopy 4
- Only 52% of positive Cologuard patients had positive findings on colonoscopy in one study, but this still represents a clinically significant detection rate requiring intervention 5
- No colorectal cancer was found in one cohort of patients with prior normal colonoscopy, but the high rate of advanced adenomas (30%) justifies the colonoscopy 4
Patient Education Points
Emphasize these key messages to patients:
- Colonoscopy is required regardless of the absence of symptoms 2
- The procedure both diagnoses and can treat polyps simultaneously 2, 3
- A positive Cologuard result mandates follow-up colonoscopy—this is not optional 6
- Many patients with abnormal stool tests are unaware of the abnormal result or face barriers to colonoscopy completion, making clear communication essential 7
Post-Colonoscopy Surveillance
If colonoscopy reveals adenomatous polyps, regular surveillance will be necessary:
- Surveillance intervals depend on polyp characteristics including number, size, and histology 2, 3
- Patients with one or more adenomas require surveillance programs to identify metachronous adenomatous polyps 3
Special Considerations for Age 45-85
For average-risk adults aged 45-85 with positive Cologuard:
- Begin colorectal cancer screening at age 45 years per current USPSTF recommendations 1
- Continue screening until age 75 years (Grade A recommendation) 1
- For adults aged 76-85 years, screening decisions should be individualized based on health status, life expectancy, comorbid conditions, and prior screening history 1
- Discontinue screening after age 85 years 1