A Telephone Intervention to Improve Participation in a Screening Program.

"A brief telephone intervention at the same time of sending the invitation letter plus the habitual invitation process used in the screening program (described in control group). Each phone call will last approximately 5 minutes.~Calls will be made by the administrative staff of the Screening Technical Office, which is experienced in telephone attention."

The habitual invitation strategy used in the screening program . Three letters are send by post: 1- An invitation letter plus an information leaflet and a list of pharmacies in which people can obtain the screening test. 2- A reminder letter for those who have not participated after 5 weeks of sending the first letter. 3- A second reminder letter for those who have collected the kit in the pharmacy but have not returned it with the sample