What is fecal genetic testing and can this test be used to replace the standard guaiac test for occult blood to screen for colon cancer?
Passage of stool through the colon leads to shedding of microscopic amounts of colonic cellular DNA that remain viable in stool for many days. Genetic mutations present in microscopic amounts in this tissue can be detected by polymerase chain reaction of stool samples. An array of genetic tests is performed to detect genetic mutations associated with colon cancer, such as APC mutation (a molecular marker for adenomatous polyps), and BAT mutation (a marker for mismatch repair gene mutations). This test is currently investigational as a screening test for colon cancer and is not commercially available. The sensitivity of a single fecal DNA test is reportedly approximately 80% for colon cancer but is much lower for advanced adenomas, a characteristic that currently limits its clinical applicability. Even so, it has a higher sensitivity than guaiac testing for detecting advanced adenomas. It is hoped that future identification of novel genetic mutations in colonic carcinogenesis will yield additional genetic tests to place in the genetic array to increase test sensitivity, especially for detecting adenomas.