Is FIT fit for purpose? 

I think it is fair to say that the recent NHS England letter to practices advising on the role of Faecal Immunochemical Testing (FIT) in the assessment of people with suspected colorectal cancer has not been universally well received and has left some GPs wondering if FIT is indeed, fit for purpose. A recent Pulse article covered the plan and received comments that included “The NHS – fobbing the patient off, via the GP scapegoat” and “This strikes me as dangerous and stupid. Another attempt at responsibility transfer?” 

If you haven’t seen the letter, NHS England are outlining new recommendations for the role of FIT, following the publication of a recent guideline from the British Society of Gastroenterology (BSG) & Association of Coloproctology of Great Britain & Ireland (ACPGBI). This also follows new guidance for the NHS in Scotland.

There are some key learning points from the NHS England guideline for those of us working in primary care which we are discussing on our current round of Hot Topics GP Update courses. First, the threshold set for a positive test in some who is symptomatic (typically 10µg Hb/g) is FAR lower than the threshold used in bowel cancer screening, which ranges between 80 to 150µg Hb/g across the UK. Take home message? We must NOT rely on a recent negative screening FIT result to exclude colorectal cancer in a patient who develops symptoms. 

Secondly, FIT is now recommended for use in patients with rectal bleeding. Previously we were advised against using FIT in this context by NICE DG30. However, recent research, such as the NICE FIT study, showed that FIT performs similarly well in patients with or without rectal bleeding. Among people referred with suspected colorectal cancer and rectal bleeding, the sensitivity and specificity of FIT were 96.6% (95%CI 92.2 to 98.9) and 76.6% (95%CI 75.0 to 78.1) respectively. People who meet the urgent referral criteria based on rectal bleeding should have an urgent colonoscopy if the FIT is positive but can be referred for a routine sigmoidoscopy if the FIT is negative. 

Third is the importance of practices developing robust procedures to follow-up on patients who are recommended a FIT, recognising some patients may not return a sample and are then at risk of having delayed investigation.

Most controversial however, has been the role FIT should play in the suspected colorectal referral pathway from primary care. NHS England is suggesting people with a negative FIT, a normal full blood and no ongoing clinical concern can be reassured without onward referral. The hope is this approach might take some pressure off over-stretched endoscopy services and enable improved triaging of urgent cases. The negative predictive value of FIT is reported to be as high as 99.8% (95%CI 99.5 to 99.9), suggesting at a population level there is justification for this approach. 

However, the sensitivity of FIT is around 90% - in NICE FIT it is reported as 86.8% (95% CI 74.7% to 94.5%) at the 10µg Hb/g threshold. This means some people with colorectal cancer will not be referred onto secondary care in a timely manner if we rely on FIT alone. In a primary care service evaluation from South-West England, 3,890 patients aged 50 years or older with low-risk symptoms for colorectal cancer had a FIT done. There were 618 positive for FIT, of whom 43 were diagnosed with colorectal cancer. However, a further 8 people were diagnosed with colorectal cancer over 12 months of follow-up among the 3,272 people with an initial negative FIT. It is worth noting these data show FIT outperforms some existing biomarkers that are central to triaging urgent referral of other cancers, such as Ca-125 and ovarian cancer.

The BSG/ACPGBI guideline recommends that people with a negative FIT but ongoing symptoms are still considered for further assessment. This may include a less urgent referral for investigation of possible colorectal cancer, repeating the FIT after six weeks, which improves the sensitivity up to around 97%, or using an Advice and Guidance service. Alternatively, patients may need an urgent referral for investigation of another cancer, such as via a Rapid Diagnostic Centre. Recent guidance for the NHS in Scotland recommends that if patients have persistent symptoms, they have a repeat FIT test within 6 weeks and are still referred even if FIT negative if they have iron deficiency anaemia or on-going clinical concern.

As GPs we should embrace FIT testing. The controversy over the NHS England letter has created a potentially dangerous negativity around the test.  The evidence is clear that FIT is ‘fit for purpose’; it outperforms many other tests we use for the earlier detection of cancer, it helps to detect cancer at an earlier stage and a negative test is indeed reassuring. So, we must try to ensure local pathways allow us to use FIT but also to understand that a negative result does not mean patients with ongoing symptoms are denied further investigation. 

We are discussing this new guidance on our current Hot Topics courses, as well as early diagnosis of pancreatic and ovarian cancer. Do come and join us!