? On Cologuard (colonoscopy, blood tests, doctor, diet)

[Charlie&Rose]

My doctor said that there is no need to avoid certain foods before doing the cologuard test. When i google it though, is says alot of foods such as red meat, fruits and veggies can trigger a positive test. I wonder if that is the reason for so many false positives. I want to make sure that I do it right. As anyone else watched their diet before the test, and has it affected the results. Thanks!

[Charlie&Rose]

Originally Posted by xkfgg

I've gotten to a point and tend to do the Opposite of what the standard type doctors tell us to do....something like the politicians advice. Good luck. I've never done any of the tests was close with the one you are talking about but never did it.

Believe me I don`t want to do it, but it would always be on my mind.....better to get it over with.

[Parnassia]

Originally Posted by Charlie&Rose

My doctor said that there is no need to avoid certain foods before doing the cologuard test. When i google it though, is says alot of foods such as red meat, fruits and veggies can trigger a positive test. I wonder if that is the reason for so many false positives. I want to make sure that I do it right. As anyone else watched their diet before the test, and has it affected the results. Thanks!

I've taken several of these tests, all negative results. I wasn't advised to and didn't do anything special in terms of diet prior. False positives are very common for multiple reasons.

[Travelassie]

Originally Posted by Charlie&Rose

My doctor said that there is no need to avoid certain foods before doing the cologuard test. When i google it though, is says alot of foods such as red meat, fruits and veggies can trigger a positive test. I wonder if that is the reason for so many false positives. I want to make sure that I do it right. As anyone else watched their diet before the test, and has it affected the results. Thanks!

The hemoglobin testing portion of the Cologuard ( the part that tests for the presence of blood in the sample) is an immunochemical test that detects only the presence of human hemoglobin in a fecal sample, it does not pick up the presence of hemoglobin from nonhuman sources ( such as that rare steak you ate the night before you did the test). The immunochemical test ( acronym FIT- fecal immunochemical test) also is not subject to the interference from other substances that might be present in the stool, such as high level of ascorbic acid ( from vitamin C), aspirin, or other oxidizing substances that might be present in the stool and could cause false positive hemoglobin results in the guiac based fecal occult blood tests. So a positive reaction in a FIT based fecal occult blood test is specific for human hemoglobin, and as your doctor says there is no need to avoid red meat or other foods, or medications before you collect a sample for the Cologuard or other FIT-based test.



The FIT test is based on detection of an antigen-antibody reaction that is specific for human hemoglobin.

The antigen is the hemoglobin that may be present in a fecal sample. The FIT test contains an IgG antibody specific for human hemoglobin, along with a dye attached to the IgG that changes to a blue color with the addition of a liquid reagent to detect the antigen-antibody reaction if there is hemoglobin ( blood) in the fecal sample.


https://medlineplus.gov/ency/patient...ons/000704.htm



What you are probably reading about in your google searches are the guiac-based occult blood tests. Guiac is a chemical that reacts with hemoglobin from any source ( such as that rare steak you ate the night before the test) so it's not specific for human hemoglobin. It's also subject to false positive results from ascorbic acid, or other oxidizing agents from fruits, veggies or meds you might have eaten shortly before the test. In the event you use a guiac based test for fecal occult blood testing, it's important to read and follow the instructions in the package insert or patient information before you collect the sample. As I recall some of these instructions include waiting for two days to test if you've eaten beef products, waiting some time if you've taken high levels of vitamin C or certain medications such as aspirin or NSAIDS.



In any case, in the event you receive an use an occult blood system ( card) for testing, it's a good idea to read the information that comes with it and follow the instructions to ensure a valid result.

[guidoLaMoto]

The Cologuard Test can detect blood in the stool or abnormal DNA associated with colon cancer.

Many colon tumors do exhibit occult bleeding, but because things like hemorrhoids, which also frequently bleed, the number of false positives (the test is positive but you don't have ca) is pretty high.

The real problem is the false negatives (you have ca but the test says you don't) is also pretty high. The rates of false pos & neg are roughly 10% for each.

If you're over 50 with no fam hx of colon ca, don't be lulled into complacency by a negative Cologuard-- Get you routine colonoscopy anyways. (Start earlier if there is a fam hx)

A smart doc will use a positive test (even tho 10% are wrong) as an incentive to convince a reluctant pt to get the colonoscopy.

Either way, there's no substitute for a colonoscopy as a screening test. I don't even see the need to do a stool guaiac or Cologuard for that reason.