Cancer in the large intestine often leaves traces of blood in stool that can’t be seen with the naked eye (occult blood). In order to verify whether you have blood in your stool or not, you must have an immunochemical fecal occult blood test (iFOBT). The results of this test will not confirm whether you have cancer or not but will tell you if you should have a colonoscopy for verification.
The iFOBT test involves taking a sample of your stool at home. The sample is then analysed in the laboratory.
The iFOBT is a screening method recommended to most people between the ages of 50 and 74 at average risk for colorectal cancer (colon and rectum).
Get a prescription from your doctor
If you are between 50 and 74 years old, ask your doctor if you should have an iFOBT. If so, your doctor will give you a prescription to get a sample collection kit.
Get a sample collection kit
Sample collection kits are available in most specimen collection centres. To find the centre nearest you, see the page Finding a resource offering laboratory tests . Call the centre to make sure that they can provide you with a kit.
Then go to the specimen collection centre with your prescription and health insurance card. The staff at the centre will provide you with a sample kit and an instruction sheet, and will explain how to collect a sample at home.
Take a sample of your stool
To obtain a sample of your stool, you need the sample collection kit and the instruction sheet provided to you at the specimen collection centre. Be sure to follow each of the steps indicated on the sheet.
Take your sample to the specimen collection centre
Take your stool sample to the specimen collection centre where you picked up your kit no later than 48 hours after collection. After your sample has been analyzed, your doctor will receive your test results and will follow up with you accordingly.
Possible test results
There are 3 possible results:
Negative test result
Your test is negative if no trace of blood is detected in your stool. In this case, your doctor may prescribe you another iFOBT in 2 years.
A negative result does not guarantee:
That you don’t have a cancer
That you will not develop colorectal cancer in the future
Hence, you should do the test every 2 years and talk to your doctor if you notice the apparition of 1 or more symptoms associated with colorectal cancer.
Positive test result
If there is blood in your stool, your test is positive. In this case, your doctor will recommend a colonoscopy.
The presence of blood in the stool is not necessarily an indication of cancer. Other health problems can also be the cause, including hemorrhoids and anal fissures.
Positive test results are uncommon. Of 1,000 people screened, only 36 will have a positive result and must then do a colonoscopy. Of these 36 people:
4 will have colorectal cancer
17 will have one or more polyps removed (small masses of flesh that look like warts; they grow on the inner lining of the large intestine)
15 will have neither polyps nor cancer
A test is inconclusive when it has been administered incorrectly, or when too much time has elapsed between the test and the analysis. If your test is inconclusive, you must take it again. It is therefore essential to follow instructions received with your sample collection kit. These instructions are also available on the Instructions for Immunochemical Fecal Occult Blood Test (iFOBT) page.