From Stool to Scope: Optimising FIT Thresholds to Guide Future Panenteric Capsule Endoscopy and Reduce Colonoscopy Burden in Iron Deficiency Anaemia

Ian Io Lei; Nicola O'Connell; Michael Agyekum Adu-Darko; Jessiya Parambil; Vishnupriya Suresh; Kiara Mc Donnell; Jessie Newville; Kirsten Chaplin; Deekshi Siyambalapityage; Asad Khan; Usman Muhammad; John Emil; Merali Abbas; Zia Kanji; Omar Khalil; Hamza Alam; Amelia Bennett; Hannah Soanes; Adrija Bhattacharyya; Karl Frey; Rosie Meakins; Archit Singhal; George Pack; Melike Gerrits; Harry Paterson; Vincent Cheung; Sue Cullen; Imran Aslam; Chander Shekhar; Ramesh P Arasaradnam

doi:10.3390/cancers17121951

From Stool to Scope: Optimising FIT Thresholds to Guide Future Panenteric Capsule Endoscopy and Reduce Colonoscopy Burden in Iron Deficiency Anaemia

Cancers (Basel). 2025 Jun 11;17(12):1951. doi: 10.3390/cancers17121951.

Authors

Ian Io Lei^{1

2}, Nicola O'Connell¹, Michael Agyekum Adu-Darko³, Jessiya Parambil⁴, Vishnupriya Suresh¹, Kiara Mc Donnell⁵, Jessie Newville⁵, Kirsten Chaplin⁵, Deekshi Siyambalapityage⁵, Asad Khan³, Usman Muhammad³, John Emil³, Merali Abbas³, Zia Kanji³, Omar Khalil¹, Hamza Alam³, Amelia Bennett⁴, Hannah Soanes⁴, Adrija Bhattacharyya⁴, Karl Frey⁴, Rosie Meakins⁴, Archit Singhal⁴, George Pack⁴, Melike Gerrits⁴, Harry Paterson⁴, Vincent Cheung⁴, Sue Cullen⁵, Imran Aslam¹, Chander Shekhar¹, Ramesh P Arasaradnam^{1

2

6}

Affiliations

¹ Institute of Precision Diagnostics & Translational Medicine, University Hospital of Coventry and Warwickshire, Clifford Bridge Rd, Coventry CV2 2DX, UK.
² Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
³ Department of Gastroenterology, Milton Keynes University Hospital, Standing Wy, Eaglestone, Milton Keynes MK6 5LD, UK.
⁴ Department of Gastroenterology, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Headley Way, Headington OX3 9DU, UK.
⁵ Department of Gastroenterology, Stoke Mandeville Hospital, Buckinghamshire Healthcare NHS Trust, Mandeville Rd, Aylesbury HP21 8AL, UK.
⁶ Leicester Cancer Centre, University of Leicester, Leicester LE1 7RH, UK.

Abstract

Background: Colon capsule endoscopy (CCE) or panenteric capsule endoscopy (PCE) offers a promising, non-invasive diagnostic approach for patients with iron deficiency anaemia (IDA). However, high rates of conversion to conventional colonoscopy (CCC) following capsule procedures reduce cost-effectiveness and patient satisfaction. Optimising the faecal immunochemical test (FIT) threshold may improve patient stratification and reduce unnecessary conversions in future applications within the IDA diagnostic pathway. Methods: The CLEAR IDA study was a multicentre, retrospective observational study conducted across four UK hospitals. Data were collected over a six-month study period and included patients referred via the two-week-wait (2WW) cancer pathway for iron deficiency, with or without anaemia, over a 12-month timeframe. Colonoscopy findings were analysed and extrapolated using NHS England's CCE-to-colonoscopy referral criteria to assess the predictive value of FIT for colorectal cancer (CRC), polyp burden, and CCC using ROC curve analysis. The optimal FIT threshold was identified through three complementary approaches: threshold-based analysis, decision curve analysis, and cost-benefit modelling. Results: A total of 1531 patients were analysed; only 1.6% underwent small bowel capsule endoscopy. The diagnostic accuracy (AUC) of FIT for predicting CRC, polypoidal lesions, and CCC was 0.78, 0.58, and 0.69, respectively. Threshold-based analysis identified FIT = 15 µg/g as the lowest level at which CCC rates significantly increased (p = 0.02; OR = 1.87; 95% CI: 1.07-3.14). Decision curve analysis showed a maximum net benefit at FIT = 17.6 µg/g, while cost-benefit modelling identified 9 µg/g as the most cost-effective. Raising the threshold to 10 µg/g resulted in a net loss of GBP -294.4 per patient. An optimal cost-effective FIT threshold range was identified between 10 and 17.6 µg/g. The threshold selection should be tailored to local service capacity and resource availability. Conclusions: While FIT alone is an imperfect triage tool, optimising thresholds between 10 and 17 µg/g may enhance cost-effectiveness and guide appropriate PCE use in IDA.

Keywords: IDA; anaemia; capsule endoscopy; colon capsule endoscopy; colonoscopy; colorectal cancer; iron deficiency anaemia; panenteric capsule endoscopy; polyp.