FIT testing, or a Faecal Immunochemical Test, tests for microscopic traces of blood in your stool. It’s a new and highly accurate test, and has two main purposes. The first is in bowel cancer screening, where you have no symptoms, and the second is to diagnose a condition based on bowel symptoms, for example, in inflammatory bowel conditions like Crohn’s disease or ulcerative colitis, or symptoms that could be bowel cancer. There can be lots of other causes for bleeding in the gut – some serious, some less so.
A positive test – that there is bleeding coming from somewhere in your gut – is used to then order further investigations that can pinpoint the cause of your symptoms, or determine whether this may be an early sign of bowel cancer.
It’s important to emphasise that this is not a test for cancer or any other disease – it only tests for blood in the gut, and this could also be from haemorrhoids, a tear in the anus, a polyp, diverticular disease, or even bleeding from high up in the gut, like a stomach ulcer. It needs further investigations within context before a diagnosis can be made.
You will receive a home test kit by post if you are within the age group to be eligible for bowel cancer screening (aged 60 to 74). Alternatively, your doctor will hand you a kit to take home and test.
A small sample of poo is collected onto a plastic stick, placed in a container and posted back to the lab for testing. Each kit has its own instructions but further information on how to do the test can be found here: https://www.gov.uk/government/publications/bowel-cancer-screening-kit-how-to-use
For bowel cancer screening, your kit should include a return envelope to send this back.
If your doctor has requested it based on symptoms, return it to your surgery, and they will send it on to the local lab. The reception staff are used to handling samples, don’t worry. You should usually expect to get a result within 1 to 2 weeks.
A negative result makes bowel cancer, otherwise called colorectal cancer, highly unlikely. You will await your next screening test in two years, but if you have concerning symptoms in the meanwhile – a change to your bowel habit, new persistent diarrhoea or constipation, weight loss, feeling very tired or any iron deficiency anaemia – then you should book an appointment with your doctor. Don’t wait until your next screening.
With a positive result, your doctor will send you on a fast-track pathway to investigate this – you will be seen at a hospital of your choice within a couple of weeks. This team will likely order a blood test and a colonoscopy, where a tube with a camera is inserted in the back passage to visualise the bowel and take any tissue samples.
As there will be a specific reason why your doctor requested this, it’s best to catch up with them to explain the results and any next steps. A negative result simply means that no bleeding was detected in your bowel. Negative or positive, your doctor may suggest further investigations to determine the cause or your symptoms, or a trial of treatment.
Your doctor may suggest a blood test or a colonoscopy. For IBD, that may suggest another stool test, called a calprotectin test.
If your symptoms could be due to bowel cancer even with a negative test, they may decide to refer you on the fast-track pathway anyway. They will use their clinical judgement.
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