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Fecal immunochemical test


This test is used to detect blood in stool that cannot be seen with the naked eye by submitting 1-3 bowel movements. A FIT is often used to detect bleeding in the digestive tract which has no other signs or symptoms. A FIT test is similar to an FOBT, except the FIT test is newer and doesn’t require a restricted diet before. A FIT test may not detect blood from further up the digestive tract (such as the stomach), which means it is more specific to finding blood coming from the lower gastrointestinal tract than the FOBT.

  • Examines stool for signs of blood
  • No prep
  • No risks
  • Inexpensive, usually covered by insurance

Advantages

  • Easy to do
  • No special changes to diets or medicines
  • Simple; not as many stool samples needed
  • No liquids/prep to drink
  • Inexpensive; covered by most insurance
  • Done in privacy of your home and flexible for your schedule
  • More specific than guaiac FOBT; identifies human blood only

Disadvantages

  • A number of tests are available; they use different antibodies and therefore differ in their sensitivities
  • Patients may find test unpleasant
  • May miss tumors that bleed in small amount or not at all
  • These tests may perform poorly without refrigeration in warm climates or if there are postal delays
  • Must be repeated every year

Will my insurance cover it?

Medicare covers FIT once a year for individuals 50 and over. Most other insurers will cover FIT as well; talk to your carrier.

The facts

The fecal immunochemical test (FIT), also called an immunochemical fecal occult blood test (iFOBT), is a newer kind of stool test that also detects occult (hidden) blood in the stool. This detection is important because it can be a sign of precancerous polyps or colorectal cancer. Blood vessels at the surface of larger polyps or cancers are often fragile and easily damaged by passing stool. The damaged blood vessels usually release a small amount of blood into the stool, but only rarely is there enough bleeding to be visible in the stool, which is why these tests are helpful.

The FIT is done essentially the same way as the traditional guaiac FOBT, though some people may find it easier since there are no drug or dietary restrictions. Since vitamins and foods do not affect the FIT, sample collection may take less preparation. There are many varieties of FIT tests with varying levels of sensitivity, and depending on which you have, it may require as few as one stool sample, instead of three, like a guaiac FOBT. This test is also less likely to react to bleeding from parts of the upper digestive tract, such as the stomach, which is beneficial in increasing accuracy.

The prep

One advantage to the FIT is that there is no preparation needed. You simply need to get the kit from your doctor and collect the sample.

The procedure

We realize this test isn’t going to be the most enjoyable experience. But there are a few ways to make your testing a little easier. First, see your doctor for the test kit. Once you’re ready, get all of your supplies ready and in one place. The kit will give you detailed instructions on how to collect the stool specimen. Always follow the instructions on your kit, but typically your test will instruct you to:

  • Lift toilet seat and position sample collection paper across rim of toilet bowl. Secure adhesive tabs to the sides of the toilet rim. Lower seat.
  • Make bowel movement onto collection paper.
  • Unscrew cap from the sample collection tube.
  • Poke applicator into stool at several sites. Screw the applicator back into the tube secure tightly.
  • Fill out the personal information on attached label on tube.

Complete the address return label and insert sample collection tube into specimen pouch and seal. Insert specimen pouch into return envelope and seal. Return the sample packet immediately by mail or in person. 

The big 'what if…'

For the FIT, a positive result indicates abnormal bleeding in the lower digestive tract. Since this test detects only human blood, other sources of blood, such as those from the diet, do not cause a positive result.

A positive result from this test requires a follow-up colonoscopy.

How often (if not high risk)

Once a year starting at age 50.

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