- Outcome variable. The outcome variable will be if the individual attended CRC screening. This will be linked to SYC data using data supplied by the National Bowel Cancer Screening Programme. It should be noted that CRC screening relates to the first time an individual is screened (prevalent screening). The main analysis will look at if an individual has had a CRC screen (irrespective of number of invitations to screening that were sent). Depending on the available evidence, a secondary analysis would consider the outcome variable of 'individual accepted CRC screening after refusing the initial invitation for CRC screening.'