The COCCOS study: A protocol for a multicentric quasi-experimental study of a healthcare transition program for young people with chronic conditions.

INTRODUCTION: The growing number of adolescents and young adults (AYAs) living with chronic conditions highlights the need for effective healthcare transition programmes (TPs) to support the transfer from paediatric to adult care. Despite existing recommendations, many AYAs experience inadequate preparation, resulting in disrupted care and adverse health outcomes. The COCCOS project developed a co-designed TP to address these challenges. This study presents the protocol for an evaluation of this programme. METHODS AND ANALYSIS: A multicentric quasi-experimental pretest-posttest study will be conducted in two Belgian university hospitals. AYAs aged 17-18 years with type 1 diabetes, asthma, or obesity will be recruited into an intervention group receiving the COCCOS TP or a control group receiving usual care. The intervention consists of four structured consultations over 13-16 months, focusing on transition preparation, autonomy, and continuity of care. Primary outcome is transition readiness, measured using the Transition Readiness Assessment Questionnaire. Secondary outcomes include patient empowerment, medication adherence, health-related quality of life, and mental health. Data will be collected at baseline, transfer, and four months post-transfer. Cost-effectiveness will be assessed from a healthcare payer perspective using quality-adjusted life years. A mixed-methods process evaluation will examine implementation fidelity, acceptability, and contextual factors through observations, surveys, and interviews. The study is registered on ClinicalTrials.gov under identifier NCT07145671. DISCUSSION AND CONCLUSION: This study will provide comprehensive evidence on the feasibility, preliminary effectiveness, cost-effectiveness, and implementation of a co-designed TP in real-world clinical practice. By integrating clinical, economic, and process outcomes, it addresses key gaps in transitional care research. Findings will inform refinement of the programme and the design of a future large-scale trial, contributing to the development of sustainable, patient-centred transition care for AYAs with chronic conditions.