The calculation of targets for the cancer and adenoma detection rates for the NHS bowel screening programme

The NHS bowel screening programme offers people aged 60-69 screening by faecal occult blood (FOB) testing, with colonoscopy as the diagnostic test. This paper describes the calculation of targets for the purpose of monitoring screening performance in the programme.

Targets were calculated for the prevalent round of screening in people aged 60-69, and for the 'steady state' of the programme when people will be offered their first screen at age 60 and subsequent screens at ages 62-69. Targets for the cancer and adenoma detection rates per 1000 people screened and per 100 colonoscopies were calculated using information from the English bowel cancer screening pilot.

For the prevalent round, prevalent screen and incident screens the calculated targets for the cancer detection rate are 2.3, 1.3 and 1.7 per 1000 people respectively. For the adenoma detection rate the targets are 6.7, 5.2 and 5.5 per 1000 respectively. Targets for the cancer detection rate per 100 colonoscopies are 11.3, 7.5 and 8.4 and those for the adenoma detection rate are 32.0, 30.4 and 32.5 respectively.

The purpose of these targets is to ensure that the national bowel cancer screening programme is effective with a high quality of screening. The cancer detection and adenoma detection rates per 1000 people are those estimated to be necessary to achieve the expected mortality reduction. Rates per 100 colonoscopies (equivalent to the positive predictive value of referral to colonoscopy) are designed to maintain a high quality of screening by minimizing the number of false-positive referrals.