Faecal Immunochemical Test (FIT)
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Bowel cancer screening reduces bowel cancer mortality. Since bowel cancer screening began in the UK, it has made use of a certain type of faecal occult blood test - a guaiac-based test (gFOBT). Now, the guaiac test is being replaced by a Faecal Immunochemical Test (FIT) test.
Here you can find information on the new test, it’s implementation and how this will affect healthcare professionals, people invited for screening, and patients.
The Faecal Immunochemical Test (FIT) uses antibodies that specifically recognise human haemoglobin (Hb). It means that a FIT result is not influenced by the presence of other blood in stools, such as that ingested through diet, compared to the guaiac Faecal Occult Blood Test (gFOBT), therefore reducing the chance of false positive results.
It is used to detect and can quantify the amount of human blood in a single stool sample. A positive FIT result suggests that there may be bleeding within the gastrointestinal tract that requires further investigation. Those with a positive result are then invited for further testing, normally colonoscopy.
The bowel cancer screening programme previously used a Guaiac Faecal Occult Blood Test (gFOBT) but this has now been replaced by the Faecal Immunochemical Test (FIT) in all nations of the UK except Northern Ireland. It is intended for people without any signs or symptoms of bowel cancer.
In Scotland, FIT replaced gFOBT as the test for bowel screening in November 2017.
In England, the implementation of FIT began in June 2019.
In Wales, FIT started to replace gFOBT through a phased roll out, with 1 in 28 people eligible for screening receiving the new kit from the end of January 2019. From September 2019, FIT completely replaced gFOBT and is the primary bowel screening test.
The Department of Health in Northern Ireland have committed to switch from gFOBT to FIT screening in early 2020.
FIT measures micrograms of human haemoglobin per gram of faeces. The definition of a positive or negative result can be changed by altering the numerical FIT threshold. As a general statement, the lower the threshold or cut-off, the more sensitive the test will be and the more cases of cancer and adenoma that will be detected and ultimately deaths from bowel cancer averted.
In Scotland, FIT was introduced with a cut-off of 80μg/g, which has a higher detection rate for advanced adenomas but a comparable cancer detection rate to gFOBT screening.
In England, FIT has been introduced with a cut-off of 120 μg/g. However, to optimise FIT, there are plans to reduce the sensitivity threshold.
In Wales, FIT has been introduced with a threshold of 150μg/g. The Welsh Government have announced that the Bowel Screening Wales programme will reduce the FIT cut-off to 80μg/g by 2023.
As with gFOBT bowel screening, GPs will be notified as to whether a person has participated in the bowel cancer screening programme and if so, whether they had a positive or negative result. GPs will not be given the numerical value of the FIT result.
Safety netting patients
- Even in patients with a negative FIT screening result, it’s important that GPs continue to be alert to the possibility of bowel cancer, as some cancers may still be missed.
- GPs should also remind people to be aware of key signs and symptoms of bowel cancer, and to seek medical advice if they notice anything new or unusual, even if they’ve recently taken part in bowel screening.
The use of FIT in bowel cancer screening in the UK has indicated improved participation.
We are starting to see an increase in bowel screening uptake as a result of FIT in England Uptake at 67.5% in Q2 (Jul-Sept 2019) .
Uptake of bowel screening in Scotland has increased from 56.2% to 64.1% for comparable 18-month periods before and after introduction of FIT . The increase in uptake after the introduction of FIT was greatest among people from more deprived areas.
While it is anticipated that FIT will make a positive contribution to bowel screening uptake, we’re still expecting it to fall short of that seen in other cancer screening programmes, and inequalities may persist. FIT will be easier for people to complete because it requires only one stool sample, but we expect patients will still experience barriers to participation that the support of their GP and wider practice team could help them overcome.
Research shows that primary care interventions can significantly increase uptake in bowel screening. The CRUK Primary Care Good Practice Guides offer practical advice to support primary care, or GPs and wider practice team to endorse bowel cancer screening.
Bowel cancer screening has harms as well as benefits, so it’s important to assist patients in making an informed decision about whether to take part. Some harms your patients should be aware of include false positives and negatives, over-reassurance following a normal result and the risks associated with follow-up colonoscopy.
GP Practices can help patients make an informed decision about participating in bowel screening:
- Ensure patient address details are up to date so that everyone gets their invitations and bowel screening kits.
- Talk to eligible patients about the bowel cancer screening test opportunistically during consultations.
- Encourage patients to read the information that comes with their kit so that they can understand more about the role of screening in detecting bowel cancer early and decide whether to take part.
- Break down practical barriers by explaining how to do the test by using our infographic (for England, Wales and Scotland). People who have not wanted to take part before may be pleased to hear that the process is simpler with FIT than with the guaiac test.
- Answer patients’ questions and concerns about bowel cancer screening and their result.
- Keep an eye on patients who have received positive results and ensure there aren’t any barriers to them taking part in the colonoscopy/further investigations.
- Remind patients that bowel screening works better if people take part each time they’re invited, even if previous results have been negative.
There are important key differences in the use of FIT for screening asymptomatic people through the bowel screening programme compared to being used to triage symptomatic patients.
For further information, see our FIT key differences infographics for England, Scotland and Wales.
In England and Wales, NICE guidance DG30 (2017) recommends the use of FIT for symptomatic patients at ‘low risk but not no risk’ i.e. those at a low probability of having colorectal cancer who did not meet the criteria for urgent suspected cancer referral.
A 10 μg Hb/g faeces is the recommended cut off to determine a positive result. In this instance, age and symptoms should have a positive predictive value between 0.1% and 3% for colorectal cancer to guide referral for this ‘low risk’ patient cohort.
NICE guidance DG30 (2017) also does not recommend FIT to be used in age-specific circumstances, but rather for people without rectal bleeding yet with unexplained symptoms.
However, locally commissioned FIT symptomatic services have applied the NG12 faecal occult blood testing age/symptom criteria as a way of targeting certain patient groups and managing both risk and demand. This remains however, a locally determined service arrangement.
NICE (NG12, 2015) and the Scottish Referral Guidelines (SRG) recommended the use of testing for occult blood in faeces for certain groups of symptomatic patients.
It is important that GPs are aware that bowel screening is still indicated for eligible patients, regardless of any previous use of FIT as a symptomatic test, such as that outlined in NICE guidance DG30 and Scottish Referral Guidelines (SRG).
FIT helps identify patients who may have adverse bowel pathology, who require colonoscopy or CT colonography. However, not all patients with colorectal cancer will have a positive FIT result and symptoms which indicate use of FIT may also reflect other types of cancer; so, persisting symptoms would still require further management and investigation, even if the FIT symptomatic test is negative.
Symptomatic patients need to be tested as per local cancer referral guidelines regardless of their participation and results in bowel cancer screening programme.
In Scotland, FIT is being used for symptomatic patients in pilot projects in many NHS Boards as either a primary care tool to inform referrals or in secondary care as a triage tool. Local guidance should be followed, and it is expected that a nationally agreed system for using FIT to investigate symptomatic patients will be implemented at later stage.
For symptomatic patients falling into the defined higher risk groups, FIT is not currently recommended, and so urgent referral remains appropriate. Research projects investigating the use of FIT for high-risk symptomatic patients are ongoing and will provide valuable evidence on this topic. More information around the use of FIT in higher risk groups will be provided here as soon as it is available.
Are you a health professional?
Contact the Early Diagnosis team if you have any questions on FIT introduction.
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