P125 Faecal immunochemical test (FIT) in primary care as a rule out test for IBD

Abstract

Introduction NICE recommends faecal calprotectin (FCP) testing as an option to support clinicians with the differential diagnosis of inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS) in adults with recent onset lower gastrointestinal symptoms for whom specialist assessment is being considered, if cancer is not suspected.1 Our local IBS pathway advocates use of FCP to support the above and is requested in secondary care. More recently faecal immunochemical test (FIT) for faecal haemoglobin concentration has been shown to safely and objectively determine a patient’s risk of significant bowel disease (SBD) (colorectal cancer (CRC), higher risk adenoma (HRA) and IBD2 and has been available to primary care in our area since July 2018. We examined all patients having both FCP and FIT testing in our centre to determine whether a negative FIT could be used as a rule out test for IBD in our population. Methods All patients over the age of 16 who had both a FIT and FCP between July 2018 and November 2019 in NHS Grampian were included in this retrospective study. Data on demographics, endoscopy and imaging results and diagnosis were collected. Results 191 (124 F, 67 M) patients from 17–90 yrs (median 47 yrs) had both a FIT and FCP. In 155/191 patients (81.2%) the FIT was performed in primary care first (median age of patient 47) before subsequent FCP in secondary care. FIT was negative ( 50) in 24/113 (21.2%) of these FIT negative patients. The final diagnosis in these FIT negative/FCP positive patients was: 7 diagnosis unclear (all had normal colonoscopy), 4 diverticular disease, 3 known/pre-existing IBD, 3 IBS, 3 bile acid malabsorption, 2 microscopic colitis, 1 Crohn’s, 1 haemorrhoids. 22/191 patients (11.5%) were diagnosed with IBD. 21/22 (95.5%) of these had a positive FIT. (n=5 10–100, n=4 201–400, n=10 > 400). This is compared to 20/22 (90.9%) who had a positive FCP. Conclusions In our population, a negative FIT is a good ‘rule-out’ test for IBD and has a similar sensitivity to FCP. An advantage of FIT is that it can also be used to rule out other SBD including CRC and HRA. FIT could therefore be substituted for FCP in our IBS pathway avoiding the need for secondary care FCP requests. Consideration should be given as to whether the NICE guidance1 should be reviewed/amended to include FIT. References Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. Diagnostics guidance [DG11]. October 2013 Mowat Cet al, 2019. Impact of introducing a faecal immunochemical test (FIT) for haemoglobin into primary care on the outcome of patients with new bowel symptoms: a prospective cohort study.