Location of SEPT9: 17q25
SEPT9 methylation can be detected using the HeavyMethyl technique.
The methylated form may be elevated in the blood in patients with:
(1) colorectal adenomas
(2) colorectal carcinoma
Possible indications for blood monitoring of SEPT9 methylated DNA:
(1) The patient is unable to undergo colonoscopy (distorted bowel, etc).
(2) The patient refuses to undergo colonoscopy.
(3) The patient has clinical findings that could be due to colon cancer but is unwilling to undergo colonoscopy due to an important upcoming event.
Combining it with a fecal blood test increases the sensitivity for detection.
Performance of the test depends on the population being tested. The larger the lesion the more likely the plasma test will be positive.
(1) The test may have false positives.
(2) The test may have false negatives, especially if a colon tumor is small.
(3) The test can detect adenomas but false negatives are common.
(4) According to Warren et al the sensitivity was 90% and specificity 88% for colorectal cancer.
