PTU-034 Getting the best out of faecal immunochemical tests and faecal calprotectin

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Abstract

Introduction

NICE DG30 recommends the use of quantitative faecal immunochemical tests (FIT) in patients at ‘low risk’ for colorectal cancer (CRC). No lower age limit is advised. Colorectal cancer (CRC) is rare under the age of 50 years representing 6% of all cases, whilst inflammatory bowel disease (IBD), is much more prevalent. In support of NICE DG11 we have successfully introduced a pathway for the use of faecal calprotectin (FC) to support the diagnosis of IBD. It is not known what the relative roles of FIT and FC are in this ‘low risk’ for CRC population.

Methods

We analysed pre-existing clinical outcome data on FC from diagnostic accuracy studies and pathway evaluations performed at York Hospital. We identified those that did not fulfil criteria for the ‘two week wait’ referral (NICE NG12: recommendations 1.3.1 to 1.3.3) and stratified them based on age and symptomatology. We calculated sensitivity and specificity of FC in each cohort and compared it with a published FIT comparator (Mowat et al 2015).

Results

2917 patient outcomes were reviewed. 1229 presented with a change in bowel habit under the age of 60 years, so fulfilling DG30 criteria. The prevalence of CRC was 0.5%. The sensitivity and specificity of FC as used in the York Faecal Calprotectin Care Pathway (≤100 mcg/g) is presented below both for CRC and for CRC, high risk adenomatous polyps and IBD combined, aged stratified. This is compared with FIT ≥10 mcg/g outcomes.

Results

Similar outcomes were obtained when combining all patients fulfilling DG30 criteria (that is including those with unexplained weight loss, abdominal pain and iron deficiency anaemia).

Conclusion

Despite the large numbers evaluated, the small numbers of patients with CRC make it difficult to draw any conclusions for a lower age limit upon which to apply DG30 and use FIT instead of FC. However when looking at combined CRC, high risk adenomatous polyps and IBD in this ‘low risk’ cohort, FC behaves similarly or better than FIT in those <50 years. As FIT is introduced in support of DG30 its performance should be benchmarked against existing FC pathways

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