In November 2017, a faecal immunochemical test for haemoglobin (FIT) was adopted as the first-line investigation in the Scottish Bowel Screening Programme. A number of our blogs have detailed the many advantages of FIT, including that the test is more specific for colorectal bleeding and is not subject to interference from dietary constituents. Importantly, only one small sample from a single bowel motion is needed. This is obtained using a user-friendly specimen collection device. Because of this, more people invited for screening actually participate, including those in traditionally “hard to reach” groups. The other three countries of the UK are also planning to introduce FIT as a first-line test in due course.
One of the benefits of FIT is that the threshold faecal haemoglobin concentration that is used to decide whether referral for colonoscopy is appropriate can be altered. The lower the threshold, the more colorectal disease is detected. We have shown that faecal haemoglobin depends on sex, age, deprivation and other factors, so there is a real possibility now to investigate whether factor partitioned thresholds would have value for participants. Further, faecal haemoglobin concentrations which are detectable, but below the threshold for referral, are directly related to future risk: other programme characteristics, such as screening interval or feedback information for the participant, could be based on the FIT result. Opportunities for improvement abound!
In addition, FIT is being rapidly rolled out for use in the assessment of patients presenting in primary care with symptoms of colorectal disease. This very different application could cut the number of inappropriate referrals for colonoscopy to secondary care, freeing up resources so that the threshold used in screening could be lowered and more early disease detected.
Professor Callum Fraser Senior Research Fellow, Centre for Research into Cancer Prevention and Screening, Honorary Professor, University of Dundee, Honorary Consultant Clinical Biochemist, NHS Tayside