• Jayne Digby, Callum G Fraser, Francis A Carey, Jaroslaw Lang, Greig Stanners, and Robert Jc Steele.
• Scottish Bowel Screening Research Unit, Ninewells Hospital and Medical School, Dundee, Scotland Centre for Research into Cancer Prevention and Screening, Ninewells Hospital and Medical School, Dundee, Scotland jaynedigby@nhs.net.
• J Med Screen. 2016 Sep 1; 23 (3): 130-4.

ObjectivesQuantitative faecal immunochemical tests (FIT) for faecal haemoglobin (f-Hb) in colorectal cancer (CRC) screening pose challenges when colonoscopy is limited. For low positivity rates, high f-Hb concentration cut-offs are required, but little is known about interval cancer (IC) proportions using FIT. We assessed IC proportions using an 80 µg Hb/g cut-off.MethodsIn two NHS Boards in the Scottish Bowel Screening Programme, f-Hb was estimated for 30,893 participants aged 50-75, of whom 753 participants with f-Hb ≥ 80 µg Hb/g were referred for colonoscopy. ICs, defined as CRC within two years of a negative result, were identified from the Scottish Cancer Registry.ResultsThere were 31 ICs and 30 screen-detected (SD) CRCs, an IC proportion of 50.8% (48.4% for men, 53.3% for women). CRC site distribution was similar between ICs and SD, but ICs were later stage (46.7% and 33.3%, Dukes' stages C and D, respectively). Of 31 ICs, 23 had f-Hb < 10 µg Hb/g, including six with undetectable f-Hb. A f-Hb cut-off of 10 µg Hb/g would have raised the positivity rate from 2.4% to 9.4%, increased colonoscopy requirement from 753 to 2147, and reduced the IC proportion to 38.3%.ConclusionsThe IC proportion was similar to that seen with guaiac-based FOBT. The later stage distribution of ICs highlights the benefits of lower f-Hb cut-offs, but with 19.4% of ICs having undetectable f-Hb, some cancers would have been missed, even with drastic reduction in the f-Hb cut-off.© The Author(s) 2015.

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