Occult Blood, Fecal, Immunoassay

Fecal occult blood is blood that cannot be immediately seen in your stool. This test, also known as a FIT or iFOBT, detects the presence of fecal occult blood, and, from the results, lets you determine the next plan of action for your health. It is important to keep in mind that a positive result does not directly mean the presence or absence of gastrointestinal bleeding or a particular condition. 

This test is considered a preliminary analysis. Because some polyps and occult blood are not uniformly distributed throughout the stool, false-negatives can occur. If you receive a positive result, you should continue with additional tests, possibly a colonoscopy or sigmoidoscopy, to determine the source of the occult blood. 

You should NOT have this test performed if you have bleeding hemorrhoids, constipation bleeding, urinary bleeding, or menstrual bleeding, as these conditions can interfere with the test results. 

How Is The Occult Blood Fecal Test Performed?

This test uses immunoassay (IA) methodology, meaning it uses antibodies to recognize blood proteins, making IA the best method for finding any hidden blood proteins. 

Because this is a fecal test, the sample collection process is a little different. When you get to your lab of choice, the technician will provide you a sterile cup for your sample to go in. There are a few techniques for collecting fecal matter, the most common being using film to catch the sample to avoid contaminating the sample with water, but the lab technician will inform you on how to provide your sample for the specific lab that you visit. 

Who Is The Occult Blood Fecal Test For?

It is recommended that people age 50 and up regularly screen for colorectal cancer, which can be done with a fecal occult test. This test is often recommended by doctors to screen for colon cancer or evaluate possible causes of anemia. If the fecal occult blood test is your only form of screening it should be taken once a year, but testing more often may be necessary depending on risk factors.

Risk factors include: 

• Family history of colorectal cancer
• Excessive alcohol use 
• Cigarette smoking 
• Obesity

Occult Blood Fecal Test Results Explained

Positive test results mean blood was found in your stool. From that point, you'll need to look into other tests to find out exactly where the blood is coming from.

Negative test results mean blood was not found in your stool. Bear in mind, occult blood is not uniformly distributed throughout the stool, so false-negatives can happen.