Haemophilia is a rare genetic disorder which, in its severe form and in the absence of treatment, can be life-threatening. Since the 1960s and the introduction of coagulation factor concentrates, the life expectancy of people with haemophilia has increased rapidly. Today, for most affected individuals, the disease is experienced as a chronic condition.

The transition process enabling adolescents and young adults (AYA) with a chronic disease to move into adult life can be complex, as they must face all the changes experienced by AYA in general, combined with issues related to their chronic condition and its management.

A successful transition involves a transfer of responsibility from parents to AYA regarding the management of their health condition, as well as the acquisition by AYA of knowledge, skills and autonomy. A difficult transition may lead to decreased adherence to follow-up or treatment, deterioration of overall health status and/or quality of life, or difficulties in entering adult life.

In this context, the national cross-sectional study TRANSHEMO was initiated in 2017. Its objective was to compare adherence to healthcare management between two groups of AYA with severe haemophilia (adolescents [for whom the transition is ongoing] versus young adults [for whom the transition may have been completed]), and to identify the determinants of this adherence. The results showed that young adults had a lower adherence rate than adolescents (82.2% vs. 61.2%, p<0.001). Among the determinants studied, being a young adult, having repeated at least one school year, and presenting psychological and emotional difficulties were factors that had a negative effect on adherence to healthcare management. However, the cross-sectional nature of the study represents a limitation that restricts causal inference. Complementing this project with a longitudinal study would address this limitation.

The results obtained from this new study (TRANSHEMO 2) may contribute to the literature by providing insights into both the determinants of sustained adherence to healthcare management among adolescents with severe haemophilia who become young adults, and the associations between these determinants.

The longitudinal design of the project will allow the establishment of a higher level of causal inference between the maintenance of adherence during the transition to adult life and its determinants, which represents a major epidemiological strength. Moreover, results addressing the issue of transition in the context of chronic diseases and derived from longitudinal studies remain scarce, making the findings of this project particularly original. Finally, haemophilia, a relatively frequent condition among rare diseases, could represent an interesting model for understanding the impact of transition in this type of pathology.

Study hypothesis The extent of the reduction in adherence to healthcare during the transition process, and/or the determinants of the maintenance of adherence identified in the longitudinal TRANSHEMO 2 project, may differ from those highlighted in the original cross-sectional TRANSHEMO project.

Specific aims

Main objective:

To compare the rate of adherence to healthcare among adolescents who participated in the TRANSHEMO project, using data collected during the original TRANSHEMO study when they were adolescents (before transition) and data to be collected as part of the TRANSHEMO 2 study when they have become young adults (after transition).

Secondary objective:

To identify the determinants of the maintenance of this adherence and the associations between these determinants, within the framework of a longitudinal study.

Inclusion Criteria:

• Young adults who participated in the TRANSHEMO project during adolescence and who are currently aged 20-29 years;
• Young adults with severe haemophilia (haemophilia A or B);
• Young adults registered in the FranceCoag registry;
• Young adults who have received the participant information sheet for the TRANSHEMO 2 project;
• Young adults who did not object to participation in the present study.

Exclusion Criteria:

• patients with comprehension difficulties;
• patients who are unable to read and/or write;
• patients who express opposition to participation in this study.

Young adults with severe haemophilia (haemophilia A or B)