Interval cancers using a quantitative faecal immunochemical test (FIT) for haemoglobin when colonoscopy capacity is limited

J Med Screen. 2016 Sep;23(3):130-4. doi: 10.1177/0969141315609634. Epub 2015 Nov 19.


Objectives: 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.

Methods: 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.

Results: 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%.

Conclusions: 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.

Keywords: Colorectal cancer; faecal haemoglobin; faecal immunochemical test; faecal occult blood test; interval cancers.

MeSH terms

  • Aged
  • Colonoscopy / statistics & numerical data
  • Colorectal Neoplasms / diagnosis
  • Colorectal Neoplasms / epidemiology*
  • Early Detection of Cancer / methods
  • Feces / chemistry
  • Female
  • Guaiac / analysis
  • Humans
  • Immunohistochemistry
  • Male
  • Mass Screening / methods
  • Middle Aged
  • Occult Blood*
  • Outcome Assessment, Health Care*
  • Predictive Value of Tests
  • Scotland / epidemiology


  • Guaiac