From the Guidelines
Cologuard is a non-invasive at-home screening test for colorectal cancer that examines stool DNA for genetic mutations and blood that may indicate the presence of cancer or precancerous polyps, and it is recommended for average-risk adults aged 45 and older who need regular colorectal cancer screening. The test is designed to detect the presence of known DNA alterations during colorectal carcinogenesis in tumor cells sloughed into stool, and it uses quantitative molecular assays for KRAS mutations, aberrant NDRG4 and BMP3 methylation, and ACTB in conjunction with a hemoglobin immunoassay 1. To use Cologuard, you collect a stool sample at home using the provided kit, then send it to a laboratory for analysis. No special diet or bowel preparation is required beforehand.
Key Features of Cologuard
- The test detects about 92% of colorectal cancers but is less effective at finding precancerous polyps (about 42%), making it less sensitive than a colonoscopy 1.
- If your Cologuard test is positive, you'll need a follow-up colonoscopy for further evaluation.
- The test is typically covered by most insurance plans including Medicare for eligible patients and should be repeated every three years if results are negative.
- Cologuard works by identifying abnormal DNA changes and blood that can occur as cells in the colon lining become cancerous or precancerous, allowing for early detection when treatment is most effective.
Comparison with Other Screening Methods
- Cologuard has been compared to fecal immunochemical test (FIT) and has been found to have better sensitivity than FIT for both CRC and advanced adenomas, but lower specificity for both endpoints 1.
- The test has been included as an acceptable screening method in the 2016 USPTF screening guidelines and the 2014 American Cancer Society's colorectal cancer prevention and early detection guidelines 1.
Clinical Use
- Cologuard is a useful screening tool for average-risk adults who need regular colorectal cancer screening, and it can help identify individuals who require further evaluation with a colonoscopy.
- The test is easy to use and does not require any special preparation, making it a convenient option for patients who may be hesitant to undergo a colonoscopy.
- However, it is essential to note that Cologuard is not a replacement for a colonoscopy, and patients who receive a positive result should undergo a follow-up colonoscopy for further evaluation.
From the Research
Overview of Cologuard
- Cologuard is a non-invasive colorectal cancer screening test that targets both human hemoglobin and specific genetic alterations 2
- It is a multi-target stool DNA test that combines NDRG4 and BMP3 DNA methylation, KRAS mutations, and haemoglobin 3
- Cologuard is approved by the US FDA for average-risk colorectal cancer screening 4
Mechanism of Action
- The test detects specific genetic alterations in the adenoma-cancer sequence, allowing for the study and development of non-invasive screening modalities 2
- It uses a combination of DNA methylation markers and mutations to detect colorectal cancer 5
Diagnostic Performance
- Cologuard has shown good diagnostic performance, but its detection accuracy remains unsatisfactory 3
- The test has a high rate of advanced adenomas on follow-up colonoscopy in patients with a previously negative colonoscopy 6
Comparison with Other Screening Modalities
- Cologuard is compared to other non-invasive screening modalities, such as faecal immunochemical test (FIT) and blood-based tests 5, 3
- It is also compared to more invasive screening modalities, such as optical colonoscopy and CT colonography 4