Cologuard is a stool-based DNA test for colorectal cancer (CRC) screening that has shown high effectiveness in detecting colorectal cancer and advanced precancerous lesions. Clinical studies report that Cologuard detects about 92-95% of colorectal cancers, including 94% of stage I and II cancers, with a specificity of approximately 94%, meaning it correctly identifies individuals without cancer or advanced precancerous lesions most of the time. However, false positives can occur, with about 13-14% of patients without cancer or advanced adenomas receiving a positive result. The test is non-invasive and recommended every three years for average-risk adults aged 45 and older, offering a convenient alternative to colonoscopy for initial screening.
Sensitivity and Specificity
- Cologuard detected 92.3% of colorectal cancers and 46.4% of colorectal cancers or advanced precancerous lesions in one major study, with specificity around 84-94% depending on the comparison test used.
- Updated data reported Cologuard Plus™ with 95% sensitivity for colorectal cancer and 94% specificity in average-risk patients aged 45-75 years.
- In patients aged 45-59, Cologuard detected 100% of colorectal cancers with high specificity (94%).
Usage and Follow-Up
- The test is non-invasive, analyzing stool samples at home for altered DNA and blood.
- A positive test prompts a follow-up colonoscopy to confirm diagnosis and remove polyps if necessary.
- A negative result gives a high certainty (99.9%) of not having colorectal cancer.
Limitations
- The test has a false positive rate, leading to some unnecessary colonoscopies.
- It has moderate sensitivity for advanced precancerous lesions compared to colonoscopy.
- It cannot replace colonoscopy for prevention but serves well as a screening tool to detect existing cancers early.
Overall, Cologuard is an effective, FDA-approved colorectal cancer screening tool that accurately detects most colorectal cancers and some precancerous lesions, with good patient adherence due to its non-invasive nature and convenience.