What You Really Need to Know about Cancer

Tuesday, May 12, 2015

Friday, August 15, 2014

Cologuard: First DNA based colorectal cancer screening test

Image of cologuard kitCologuard is an in votro colon cancer screening test that integrates both stool DNA and fecal immunological test techniques. It is designed to analyze person’s stool sample for DNA markers associated with the presence of Colorectal cancer and pre-cancerous cells or adenoma. After 15 years of research EXACT SCIENCES has developed this technique and has done a comprehensive research on its effectiveness before FDA approval.

Click here to read more about warning signs of Colon Cancer

Cologuard indication for use

colorectal cancer
Cologuard is indicated for the use of screening test for the recognition of Colorectal cancer associated with DNA markers to check for the presence of occult hemoglobin in stool. Cologuard is not a replacement of present colon cancer investigation Colonoscopy. It can be done along with colonoscopy according to the screening guidelines. It is more indicated for people who have high risk of having colon cancer.

Cologuard screening procedure

There are three steps involved in screening with Cologuard. They are:
  • Collection of stool by patient using stool collecting kit.
  • Analyzing stool sample in the laboratory
  • Application of an algorithm that produces positive or negative results.
The sample collection kit comes with all necessary tools including instruction for use or user manual, stool collection container, a preservative solution, protein sample tube with stool collection stick and buffer.

Cologuard Principles of operation

cologuardCologuard detects markers of altered DNA present in the cell shed by the cancerous cells and polyps in large intestine. Those markers are released from the cells that regularly and continuously slought from the lining of the large intestine into the stool. Cologuard has ability to detect the very few amount of DNA markers to identify Colorectal cancer.

Cologuard is able to identify three independent families of DNA markers that exhibits additive relationship with Colorectal cancer and pre-malignant Colorectal cancer.
  1. Targets epigastric changes in the form of gene promoter region methylation.
  2. Targets specific point mutation
  3. Family of markers is non-DNA based and detects hemoglobin in the fecal sample
Image of cologuard kit
In addition, the molecular assay component of Cologuard is used to access the genes NDRG4 and BMP3 for irregular methylation. It is also designed to measure methylation in a range of CpG sites in NDGR4 and 8 CpG sites in BMP3 promoter regions. The mutation assay component of Cologuard detects seven common KRAS mutations at codons 12 and 13. Mutant KRAS gene plays a key role in the development of Colorectal cancer in that it is a key activator in Colorectal tumorigenesis. As such, KRAS mutations afford a valuable marker for the recognition of Colorectal cancer.

The hemoglobin assay component of Cologuard is done to detect the existence of fecal hemoglobin, which can show blood loss in the gastrointestinal tract from cancerous tumors or polyps that bleed intermittently into the intestine.


With this new invention, now we can do Colorectal cancer screening at home and we can post sample to hospital with the postal form included in Cologuard kit. This is a very feasible and reliable way to detect early Colorectal cancer. Cologuard, Colorectal cancer screening is recommended for people of age 50 and above for both sex and it’s highly recommended for people who are at higher risk of developing Colorectal cancer.

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