Colonoscopy is the gold standard for the diagnosis and resection of preneoplastic lesions, allowing the prevention of colon cancer. A colonoscopy is more efficient with proper preparation of the colon, as it allows for a higher rate of adenoma detection and cecal intubation. In routine practice, up to 30% of colonoscopies are poorly prepared and 11% of patients do not show up for their appointment. Adenomas not visualized in the initial colonoscopy due to poor preparation reached 68% and the rate of undetected cancers was 66.7%. A proper colon cleanse is conditioned by different factors; among them, failure to comply with the diet and take laxatives poses 5 times the risk of having a deficient colon preparation. The purpose of our study is the design and implementation of an app that facilitates the preparation of colonoscopy and evaluates its impact on compliance with diet and laxative intake.

STUDY DESIGN AND METHODS

Study Design:

Phase 1: Design of the mobile application (APP): The APP will be designed in a participatory manner by the research team of the project, formed by doctors, nurses, statisticians and telecommunications engineers. The application should be usable with both Android and iOS devices, so we will use the Flutter framework to build apps for different platforms with a single code base.

When arranging a colonoscopy, the patient will install the APP on their mobile phone and indicate the date and time of the test. The APP will be responsible for supporting the preparation of the colon cleansing, for which, in addition to being able to visualize the corresponding information, it will make use of notifications to show diet reminders and laxative intakes.

More specifically, these could be some notifications:

• (3 days before the appointment) - Notification of start of preparation with a low fibre diet
• (24 hours before the appointment) - Notification of .laxative intake..

The APP will also consider the comorbidities and drugs of each participant. It can be adapted to the different types of laxative (4, 2 or 1 litre) and notify the need to discontinue anticoagulant and/or antiplatelet treatments by contacting with the primary care physician. Additionally, the application may ask short questions to control the laxative intake instruction. The user must confirm the appointment 48 hours in advance. The design of the APP aims to be intuitive and easy to use by the target population (50-69 years), allowing to adapt the font size and zoom in on the images to facilitate the visualization of the information.

The APP will be multilingual for English and Spanish, and others may be incorporated if deemed necessary. An agile and iterative methodology of software development will be followed as SCRUM in the realization of the APP. Thus, sprints of about 3 weeks will be planned with delivery of functional software that will progressively incorporate the different functionalities planned for the APP.

Phase 2: Re-evaluation of the APP after the inclusion of 30 patients, the APP will be re-evaluated through a usability questionnaire and adjustments and changes will be made if necessary

Phase 3: Prospective, multicentre and randomized study in asymptomatic patients between 50 and 69 years who attend screening colonoscopy after a positive FIT >100 ng / ml)

The study will be carried out in the Digestive Service of 3 hospitals in Castilla y León: Virgen de la Concha Hospital in Zamora, Medina del Campo Hospital and Río Hortega University Hospital in Valladolid. Participants will be randomized into two groups according to the instructions given to perform the preparation of the colon prior to colonoscopy: group A: perform the preparation with the written instructions delivered in the consultation and group B: the investigators will give the instructions in writing and will also indicate how to install the APP to the participants.

Inclusion Criteria:

• -Subjects between 50-69 years old from the CRC screening program with FIT (>100ng/ml).
• Informed consent granted in writing

Exclusion Criteria:

• Refusal to give informed consent.
• Those who do not have a smartphone with a minimum version of the operating system (Android 4.4 or iOS 14, which cover more than 99% of the terminals in use)
• Symptomatic patients
• Subjects at elevated risk of CRC due to family history or inherited polyposis diseases or inflammatory bowel disease

Patients who agree to participate in the study are randomized by a 1:1 block computer program (an attempt will be made to balance the groups according to the type of laxative) into two groups: group A: control group, which receives the standard information given in writing, and group B: APP group, which receives the standard information together with the mobile application individually adapted to the scheduled colonoscopy appointment and the type of laxative.

Patients scheduled for a screening colonoscopy will be contacted by telephone, those who agree to participate will be scheduled with the nurse, after giving their consent they are randomized. Group B will indicate how to download the APP and its management. The endoscopist performing the examination is blind for randomization and will assess colon cleansing according to the Boston Bowel Scale (Lai EJ. et al Gastroinest Endosc 2009).