Abstract Background Symptom-based triage systems can be unreliable in deciding which patients require colonoscopy. Faecal calprotectin (FC), is thus often used to guide referrals, as it rises in inflammatory bowel disease (IBD) due to neutrophilic infiltration of intestinal mucosa (1). Although its role as a screening tool for IBD is debated, FC shows a sensitivity of around 93% and specificity of 94% in distinguishing IBD from non-inflammatory conditions (2). The British Society of Gastroenterology (BSG) recommend local audit to guide the FC threshold for endoscopy referral (3). In the Western Trust, FC values 50µg/g make IBD unlikely, 50-150µg/g warrant repeat testing after two weeks and values 150µg/g suggest IBD and prompt onward referral. This retrospective study of 8,264 patients in the Western Trust aimed to establish the FC level most strongly associated with positive colonoscopy findings. Methods A retrospective observational study was conducted on patients who had a colonoscopy between 2022 and 2024. Reports were reviewed using the Northern Ireland Electronic Care Records (NIECR) to compare referral reasons, colonoscopy findings and FC levels. Referral reasons included raised FC (50µg/g), altered bowel habit (ABH), per rectal (PR) bleeding, IBD screening, Iron deficiency anaemia (IDA) workup, and polyp or cancer screening. Colonoscopy findings were categorised as polyps, diverticulosis, haemorrhoids, known IBD, non-specific inflammation, tumours, new IBD or normal. Results Referral reasons were polyp or cancer screening (3,060), ABH (2,058), PR bleeding (1,627), IDA workup (446), raised FC (413), and IBD screening (660). Colonoscopy findings were coded as polyps (2,959), diverticulosis (1,736), haemorrhoids (941), known IBD (453), non-specific inflammation (248), tumours (161), new IBD (63), and normal results (1,689). Among the 413 patients referred for raised FC, 25 (6%) were newly diagnosed with IBD (average age 46). The remaining 38 new IBD cases arose from other referral categories, including PR bleeding (12), IBD screening (8), ABH (9), cancer screening (5) and IDA workup (4). 70% of new IBD patients had FC levels 300µg/g. Of the remaining 350 patients referred for raised FC who did not have IBD, colonoscopy showed haemorrhoids in 43, diverticulosis in 98, polyps in 62, non-specific inflammation in 24, tumours in 7 and normal findings in 116. Conclusion Although FC levels above 300 µg/g are associated with IBD, elevated results are also seen in a substantial proportion of patients with non-inflammatory findings. FC should thus be interpreted in the overall clinical context rather than as an isolated indicator. Locally validated FC thresholds are therefore essential to ensure appropriate use of endoscopy services. References: 1. Røseth AG, Aadland E, Grzyb K. Normalization of faecal calprotectin: a predictor of mucosal healing in patients with inflammatory bowel disease. Scand J Gastroenterol. 2004;39(10):10171020. 2. van Rheenen PF, van de Vijver E, Fidler V. Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. BMJ. 2010;341:c3369. 3. British Society of Gastroenterology. Faecal calprotectin testing and its use in primary care. BSG Clinical Guidelines. 2018. Conflict of interest: Dr. Hosty-Blaney, Fearghal: No conflict of interest McGettigan, Áine: No conflict of interest Adepbote, Anne: No conflict of interest Corry, Áine: No conflict of interest Neil, Hannah: No conflict of interest Lappin, Marianne: No conflict of interest Mohamed, Miada: No conflict of interest McGoran, John: No conflict of interest Tawfik, Ahmed: No conflict of interest
Hosty-Blaney et al. (Thu,) studied this question.