Faecal Immunochemical Test
The test is used to screen for bowel cancer especially as part of the National Bowel Cancer Screening Programme. Outside of the Screening Programme the test is also widely available to GPs following the publication of the NICE Guidelines on the recognition of suspected cancers (NG12). Patients with symptoms that are suspicious of gut cancer will usually be asked to complete a FIT test before being referred for other investigations such as colonoscopy.
One sample of faeces collected into a special container.
You collect a sample yourself, in the privacy of your own bathroom, using a special kit. The actual collection method varies between manufacturers. Read all the instructions very carefully before starting to collect your sample.
For the FIT test, there are no dietary, drug, or dental procedure restrictions. However, avoid collecting samples during a menstrual period. The test uses antibodies to detect only human blood from the lower digestive tract (colon).
For all tests, follow the instructions that are provided by the doctor or included in the test kit.
The faecal immunological test (FIT) checks for blood in your faeces. Normally, there will not be enough blood lost through the gastrointestinal tract (stomach and intestines) to have a positive FIT test or for you to notice it by looking. Any significant amount of blood being passed (seen as bloody or dark, tarry faeces) should be investigated.
A positive FIT test will tell your doctor that you have bleeding occurring somewhere in your gastrointestinal tract. This blood loss could be due to ulcers, diverticulitis, bleeding polyps, inflammatory bowel disease, haemorrhoids (piles), from swallowed blood due to bleeding gums or nosebleeds, or it could be due to benign or malignant tumours. Anything that sticks out into the intestine, like a polyp or tumour, and is rubbed against by the faeces as it passes through, has the potential to bleed now and again. Often this small amount of blood is the first, and sometimes the only, symptom of early bowel cancer, making the FIT a valuable screening tool.
How is it used?
The main use for the FIT test is as a screen for early bowel cancer. Blood in the stool may be the only symptom of early cancer. If the cancer is detected before it metastasises (spreads to other areas), there is a greater chance it will be cured. A positive FIT test does not necessarily 'prove' that you have cancer. There are other possible causes of bleeding and other follow-up procedures will need to be done to find the source of the bleeding.
When is it requested?
Faecal occult blood tests may be done as part of a range if investigations if your doctor suspects that your symptoms suggest that you may have cancer. This test is also used as a screening tool for early detection of bowel cancer. The FIT test is used in the National Bowel Cancer Screening Programme. This programme offers screening every two years to all men and women aged 60 to 74 in England, Wales and Northern Ireland (50 to 74 in Scotland). People within the age range are automatically sent an invitation and test kit. From April 2021, the National Screening Programme will begin to invite younger people as part of the roll out of an age-extension programme, which will eventually lead to all men and women in England being invited every two years between the ages of 50-74.
What does the test result mean?
The FIT test is normally negative, with the cut off for a positive result differing between laboratories. Please consult your results for the cut-off in use within your local laboratory. In a patient with symptoms, a result of >10 ug/g faeces is a positive result. A positive result indicates blood in the stool and further investigation is required to identify the source of the bleeding.
What kind of procedures might follow a positive faecal occult blood test?
Before or after you have a FIT test, you may have a rectal examination. A positive FIT test may be followed by imaging tests to determine the source of the blood:
- Sigmoidoscopy: an examination of the rectum and lower colon (part of the intestines) with a lighted instrument to look for abnormalities, such as polyps
- Colonoscopy: a more thorough examination of the rectum and entire colon
Should I buy and use self-testing FIT/FOB kits which are available in some chemists?
The devices available in chemists detect blood in faeces using several different methods. Their sensitivity to detecting blood can vary and without the skills of either an experienced laboratory or doctor the results of these tests can be misleading. Consult your GP if you are concerned and think you need a test performed.