title: Interval cancers using a quantitative faecal immunochemical test (FIT) for haemoglobin when colonoscopy capacity is limited.
abstract: Quantitative 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.
  
  
  
  In 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.
  
  
  
  There 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%.
  
  
  
  The 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.
authors.affiliation: 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.
authors.forename: Jayne
authors.initials: J
authors.lastname: Digby
authors.affiliation: 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.
authors.forename: Callum G
authors.initials: CG
authors.lastname: Fraser
authors.affiliation: Department of Pathology, Ninewells Hospital and Medical School, Dundee, Scotland.
authors.forename: Francis A
authors.initials: FA
authors.lastname: Carey
authors.affiliation: Information Services Division, NHS National Services Scotland, Meridian Court, Glasgow, Scotland.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Lang
authors.affiliation: Information Services Division, NHS National Services Scotland, Meridian Court, Glasgow, Scotland.
authors.forename: Greig
authors.initials: G
authors.lastname: Stanners
authors.affiliation: 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 Medical Research Institute, Division of Cancer, Ninewells Hospital and Medical School, Scotland.
authors.forename: Robert Jc
authors.initials: RJ
authors.lastname: Steele
mesh_terms: D000368:Aged; D003113:Colonoscopy / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D055088:Early Detection of Cancer / Q000379:methods; D005243:Feces / Q000737:chemistry; D005260:Female; D006138:Guaiac / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009780:Occult Blood; D017063:Outcome Assessment, Health Care; D011237:Predictive Value of Tests; D012606:Scotland / Q000453:epidemiology
chemical_list: D006138:Guaiac
keywords: Colorectal cancer; faecal haemoglobin; faecal immunochemical test; faecal occult blood test; interval cancers