FIT for Symptomatic Assessment

Differentiating patients with serious bowel disease from those with benign functional disorders, such as Irritable Bowel Syndrome (IBS), and minor colorectal disease such as haemorrhoids, hyperplastic polyps and simple Diverticular disease, can be very challenging since the symptoms are very common and overlap in these conditions.

To date cliniciansColon_Cancer_diagnosis have usually referred patients presenting with lower gastrointestinal symptoms for further investigation via colonoscopy, creating an escalating demand for these services. A colonoscopy is an invasive procedure with associated risks and it can be stressful and unpleasant for the patient. Colonoscopies tie up significant healthcare resources and are costly.

Consequently endoscopy services are struggling to cope with increasing demand. In addition there is currently a low conversion rate to cancer in all symptomatic pathways i.e. colonoscopies are being conducted on a large numbers of patients who don’t have cancer.

NHS England spent approximately £178.4 million during 2014 on performing colonoscopies (based on NHS tariff price), yet with approximately 40% of those no pathologies were found. Identifying and prioritising those patients more likely to require urgent intervention could save significant costs, reduce waiting times and improve care.

‘There is evidence to suggest that triage using FIT at a cut-off around 10 μg Hb/g faeces has the potential to correctly rule out CRC and avoid colonoscopy in 75–80% of symptomatic patients. (Westwood et al. 1)’

NICE Diagnostics Guidance DG30

In July 2017 the National Institute for Health and Care Excellence published NICE Guidance DG30 “Quantitative faecal immunochemical tests to guide referral for colorectal cancer in primary care”

This focuses on the peer reviewed data for faecal immunochemical tests (FIT). Using this, the Diagnostics Advisory Committee created an economic model for each of the FIT methods under review. NICE DG30 recommends FIT for adoption in primary care to guide referral for suspected colorectal cancer in people without rectal bleeding who have unexplained symptoms but do not meet the criteria for a suspected cancer pathway referral outlined in NICE’s guideline on suspected cancer  (recommendations 1.3.1 to 1.3.3).

It advises that results should be reported using a threshold of 10 micrograms of haemoglobin per gram of faeces to define the threshold for ruling out colorectal cancer. The ability to use a simple, easy to use, inexpensive diagnostic test will provide additional assistance in determining the appropriate patient pathway for further investigation.

Colon-Normal-to-Cancer

FIT may have a wider role as an objective triage tool in all symptomatic patients referred from primary care. The guidance also recognises that FIT detects a symptom of colorectal cancer (haemoglobin) that could also be associated with a range of other conditions. Data from studies reporting diagnostic accuracy for multiple target conditions in the same population, suggested that up to 28.9% of people with a false positive FIT result for colorectal cancer, did have some form of serious bowel pathology, such as inflammatory bowel disease or high risk adenoma.

The guidance concludes that it is plausible that the number of false-positive results that occur when using the tests to rule out colorectal cancer, could be partially offset by detecting other treatable bowel pathology.

In the NICE DG30 Evidence Review

HM-JACKarc was reported with 100% sensitivity, 76.6% specificity, 6.1% positive predictive value and 100% negative predictive value for colorectal cancer.

NICE DG30 States:

“[FIT] assays were also cost effective when compared with no triage, with the HM-JACKarc dominating (that is, it was more effective and less expensive)”

Reference

  1. Westwood M et al. Faecal immunochemical tests (FIT) can help to rule out colorectal cancer in patients presenting in primary care with lower abdominal symptoms: a systematic review conducted to inform new NICE DG30 diagnostic guidance. BMC Medicine 2017 15:189