Evaluation of a Treatment Program for Eating Disorders That Combines Face-to-face Cognitive Behavioural Treatment With an Online Intervention Using the TCapp Application, Within the Framework of Broader Research Project Entitled mHealth: Challenges and Opportunities for Health Systems

1. The TCApp application TCapp is a tool intended to connect patients and therapists in the time between medical consultations. It is currently available on Google Play and Apple Store markets, there are more than 412 patients who are currently using it and it was developed in collaboration with different public and private mental health institutions in the Barcelona area (Althaia, Hospital de Sant Rafael, CST, ITA and Hospital Sant Joan de Déu). TCApp was designed from the start with therapists' and patients´ needs and interests in mind. By using TCapp, patients and therapists are in continuous contact, allowing for a quicker reaction from the therapist according to the patients' needs.

With TCApp, patients can record their thoughts, behaviors, emotions and whatever the therapists consider relevant for the therapy, since the app can be customized according to the therapy requirements of each specific patient. It involves algorithms based on artificial intelligence that can generate alarms when strategic words (i.e. suicide, death, etc.) are written. It also introduces technologies that allow for real-time online contact with therapists and gamification aesthetics that include prizes, rewards and reminders aimed at improving patients' engagement.

The BackOffice tool for therapists is a web-based platform where therapists can see in real time what their patients have registered (i.e. generation of graphs in a period of time to visualize parameter comparison and patient evolution) and they can interact in real time with them by using PUSH notifications. The tool is integrated in Azure server in order to ensure accordance with the most restrictive data protection laws and it is prepared for for its integration in the local management systems of hospitals and clinics. Finally, there is currently no application available to provide the same services and benefits as TCapp as most of the available applications contain self-help functionalities, rather than allowing for a bidirectional link between the patient and the therapist.

Once TCApp has proven to be an efficient and effective tool for use in ED units of public and private mental health services in Spain, the long-term contributions of the current study are as follows:

• To promote the clinical use of TCApp in ED units not only in Spain but also at an international level.
• Reduce the direct and indirect costs associated with the treatment of eating disorders.
• Improve the quality of patient care and the treatment effectiveness for EDs (e.g., increase patients' adherence to treatment, prevent relapse) while reducing waiting lists at various hospitals from Spain.
• Explore the future export of the application to other mental disorders whose treatment is also based on cognitive behavioural therapy, such as depression, addictions and anxiety.

2. Work plan and duration of the project 2.1 Methods 2.1.1 Sample The total sample will include approximately 250 patients with an ED diagnosis currently receiving treatment, who will be recruited from different public and private mental health services in Spain (Parc Taulí Hospital, Sant Joan de Déu Hospital, Dexeus University Hospital of the Quirónsalud group in Barcelona, Sant Rafael Hospital, Servei Salut de les Illes Balears and Infantil Universitario Niño Jesús de Madrid). All patients will receive standard CBT treatment, which includes the support of a multidisciplinary team from the different ED units (psychiatry, psychology, nutrition, nursing).

The a priori sample size calculation was based on results from previous studies that implemented Internet-based programs in the treatment of EDs (Aardoom et al., 2013; Hötzel et al., 2014; Ruwaard et al., 2013). A small between-group effect size (Cohen' s d = 0.40) is expected. The calculation was conducted by the software program G*POWER. The primary analysis will concern the hypothesis that the average level of eating pathology at post-intervention in the control group, based on the EDE-Q scores, will be significantly higher than the average levels of eating pathology in the experimental group. Assuming an alpha of 0.05 and a power of 0.80 (β -1) in an independent samples one-way t-test, a minimum of 100 participants would be required per study arm. Allowing for a dropout rate of 25% of study participants from the baseline, 250 participants need to be recruited in total.