Objective Faecal immunochemical tests (FIT) are replacing guaiac faecal occult blood tests (FOBT) in colorectal cancer (CRC) screening. Data from the first year of FIT screening were compared with those from FOBT screening and assumptions based on a pilot evaluation of FIT.
Design Data on uptake, positivity, positive predictive value (PPV) for CRC and higher-risk adenoma from participants in the first year of the FIT-based Scottish Bowel Screening Programme (n=919 665), with a threshold of 80 µg Hb/g faeces, were compared with those from the penultimate year of the FOBT-based programme (n=862 165) and those from the FIT evaluation (n=66 225).
Results Overall, uptake of FIT was 63.9% compared with 56.4% for FOBT. Positivity was 3.1% and 2.2% with FIT and FOBT; increases were seen in both sexes, and across age range and deprivation. More CRC and adenomas were detected by FIT, but the PPV for CRC was less (5.2% with FIT and 6.4% with FOBT). However, for higher-risk adenoma, PPV was greater with FIT (24.3% with FIT and 19.3% with FOBT). In the previous FIT evaluation, uptake was 58.5% with FIT compared with 54.0% with FOBT; positivity was 2.5% with FIT and 2.0% with FOBT.
Conclusion Transition to FIT from FOBT produced higher uptake and positivity with lower PPV for CRC and higher PPV for adenoma. The FIT pilot evaluation underestimated uptake and positivity. Introducing FIT at the same threshold as the evaluation caused a 67.2% increase in colonoscopy demand instead of a predicted 10%.
- colorectal cancer
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Contributors GRCC collected and analysed the data, contributed to writing the paper. JAS supervised the laboratories that analysed the gFOBT and FIT in the SBoSP and contributed to writing the paper. FAC provided the necessary pathology data and contributed to writing the paper. TGG assisted with analysing and validating the data. AI was Scottish Bowel Screening Services Manager and contributed to writing the paper. AMcP was Associate Service Manager, Scottish Bowel Screening Laboratory and contributed to writing the paper. JB is SBoSP Manager and contributed to writing the paper. ASA contributed on dietary issues and contributed to writing the paper. CGF was formerly supervisor of the SBoSP laboratories and contributed significant intellectual input into the writing of the paper. RJCS is Clinical Director of the SBoSP and wrote first and final draft of the paper.
Funding The FIT pilot and subsequent roll-out of FIT in the SBoSP was funded by Scottish Government.
Competing interests CGF undertook consultancy with Immunostics Inc, Ocean, New Jersey, USA, and Hitachi Chemical Diagnostic Systems Co, Ltd, Tokyo, Japan.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Data may be available following consultation with Professor RJC Steele, corresponding author.