Faecal immunochemical tests (FIT), a type of faecal occult blood test, are designed to detect small amounts of blood in stool samples using antibodies specific to human haemoglobin
- been developed as an alternative to guaiacbased faecal occult blood tests, which involve using chemicals that react with the haem component of haemoglobin in the blood and produce a blue colour change if blood is detected.
- sometimes, this colour change can happen because the chemicals react with food in a person's diet or with medicine that a person is taking; this can lead to false test results
- faecal immunochemical tests are designed to specifically detect human haemoglobin, they may give more accurate test results than guaiac-based tests
- target the globin component of haemoglobin, which degrades as it travels through the gastrointestinal tract, so these tests are less likely to detect globin from upper gastrointestinal bleeding.
NICE have stated that (1):
- Quantitative faecal immunochemical testing (FIT) using HM-JACKarc or OC-Sensor is recommended to guide referral for suspected colorectal cancer in adults
- with an abdominal mass, or
- with a change in bowel habit, or
- with iron-deficiency anaemia, or
- aged 40 and over with unexplained weight loss and abdominal pain, or
- aged under 50 with rectal bleeding and either of the following unexplained symptoms:
- abdominal pain
- weight loss, or
- aged 50 and over with any of the following unexplained symptoms:
- rectal bleeding
- abdominal pain
- weight loss, or
- aged 60 and over with anaemia even in the absence of iron deficiency
- FIT should be offered even if the person has previously had a negative FIT result through the NHS bowel cancer screening programme. People with a rectal mass, an unexplained anal mass or unexplained anal ulceration do not need to be offered FIT before referral is considered
- refer adults using a suspected cancer pathway referral (as outlined in NICE's guideline on suspected cancer) for colorectal cancer if they have a FIT result of at least 10 micrograms of haemoglobin per gram of faeces
- for people who have not returned a faecal sample or who have a FIT result below 10 micrograms of haemoglobin per gram of faeces:
- safety netting processes should be in place
- referral to an appropriate secondary care pathway should not be delayed if there is strong clinical concern of cancer because of ongoing unexplained symptoms (for example, abdominal mass)
NICE urgent colorectal cancer guidance:
- Refer people using a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer if:
- they are aged 40 or over
- with unexplained weight loss and abdominal pain
- or they are aged 50 or over
- with unexplained rectal bleeding
- or they are aged 60 or over with:
- iron-deficiency anaemia or
- changes in their bowel habit, or
- tests show occult blood in their faeces (for who should be offered a test for occult blood in faeces see below)
- a suspected cancer referral (for an appointment within 2 weeks) should also be considered for:
- people with a rectal or abdominal mass
- adults aged under 50 with rectal bleeding and any of the following unexplained symptoms or findings:
- abdominal pain
- change in bowel habit
- weight loss
- iron-deficiency anaemia.
NICE criteria for requesting test for occult blood in faeces (FIT):
- should be offered to adults without rectal bleeding who:
- are aged 50 or over with unexplained:
- abdominal pain or weight loss
- or are aged under 60 with:
- changes in their bowel habit or
- iron-deficiency anaemia
- or are aged 60 or over and have anaemia without iron deficiency
Reference: