Friday, 7 July 2017


Age should be recorded as the age of the person at the time of the invitation (for measurement of coverage/participation) or at time of screening (for measurement of screening outcome) for the respective screening round. The outcome of the screening examination for a person should thus be recorded in the same age category throughout a particular screening episode.

Screening performance indicators will also be affected by the background incidence in the target population in the absence of screening. Efforts should therefore be made to document age-gender specific incidence rates in the target population for the period immediately prior to the introduction of the screening programme. 

If high-risk subjects are identified, managed, and/or excluded from the programme and reported separately, this should be stated.

 Performance indicators will also vary according to whether the screen is a prevalent (first) screen for those invited for the first time, an incident (repeat) screen for those previously screened at the routine interval, or a screen for previous non-responders. Indicators at subsequent rounds will vary according to the screening interval.  

Only the first organised screening round will consist entirely of subjects invited and attending for the first time; all additional rounds will comprise subjects falling into each of the categories described above. The cut-off point for separating ‘subsequent regular’ from ‘subsequent irregular’ screening should be established, taking into consideration that most programmes do not succeed in inviting each individual participant at the routine screening interval (e.g. a cut-off point at 30 months for a programme with a 2-year screening interval).

Data should be analysed separately for those invited/screened at:

  •  initial screening, i.e. the first invitation of individual people within the screening programme, regardless of the organisational screening round; 
  •  subsequent invitation for previous never responders;
  •  subsequent invitation for those previously screened6 ; 
  •  screens as a result of self-referral (defined as people requesting screening before reception of an invitation or outside the invited age range); 
  • and screened following self-registration (those not recorded in target population).

For the majority of indicators the published values will have been influenced by the screening policy adopted in the respective trials and programmes. Other than those related to participation, the values reported here have therefore not been used to define acceptable levels.

There are a large number of possible process indicators, reflecting specific parts of the screening process. The present outline is confined to those that have epidemiological importance as identified within the trials. They measure participation, quality, efficacy, and organisation. Except for measures of participation, all other indicators are presented separately for in vitro tests (FOBT) and for endoscopic tests (FS or colonoscopy). 

 Coverage and uptake, i.e. participation are organisational parameters that apply to CRC screening programmes using any kind of primary screening test.

Coverage by invitation 
Coverage of the screening programme by invitation is the extent to which the invitations sent out by the screening programme within the defined screening interval include the eligible population. It gives information on the performance of the organisation of the programme in inviting the target population within the defined screening period.

N people invited during the time frame
* N eligible people in the target population during the time frame* 
* equal to the defined screening interval or reporting period, e.g. 12 months in the case of yearly reporting. 

 Coverage by examination
Coverage of the screening programme by examination is the extent to which screening examinations have actually been delivered to the eligible population.

Screened here is defined as people tested at least once regardless of whether the result was adequate or inadequate and includes self referrals but not self registrations. The latter should be counted but reported separately. Coverage of the target age range for invitation will by definition exclude self referrals outside the age range. This is important in programmes where no comprehensive population lists are available and self referral or self registration can account for a large proportion of subjects screened.

Both of the coverage indicators (by invitation and examination) are useful at a local level to assess completeness of population lists and target population’s database.  

N screened/tested during the time frame* 
N eligible people in the target population during the time frame* 
* equal to the defined screening interval or reporting period 

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