Successful Transition from Paediatric to Adult Care in Sickle Cell Disease: An Experience in a Belgian Center
Authors: Vandergraesen Tracy , Dedeken Laurence , Efira Andre , Lê Phu Quoc , Huybrechts Sophie , Diallo Safiatou , Devalck Christine , Heijmans Catherine , Azerad Marie-Agnes , Ferster Alina 
Published: October 2019

Abstract
Introduction
Despite reduction of mortality during childhood, young adults with SCD are at higher risk of morbidity and mortality after transition from paediatric to adult care, mainly in the US. To evaluate our transition system, we have studied the outcome of patients beyond the transition to adult care and looked if it was associated with an increase in vaso-occlusive crisis (VOC) and acute chest syndromes (ACS), the occurrence of progressive organ damage and changes in hydroxyurea prescription.
Patients and Methods
This study focus on sickle cell disease patients, born after January 1, 1980 and who have been transitioned from pediatrics (Hôpital Universitaire des Enfants Reine Fabiola, HUDERF) to adult care (CHU Brugmann), followed for minimum 2 years at HUDERF and having transitioned at least 2 years before December 2015. Demographic data, genotype, disease modify therapies, biological data, clinical data, acute clinical event, 6 minutes-walk test, cardiac echography) were collected retrospectively. Patients who underwent a hematopoietic stem cell transplantation were excluded from the analysis. Student test was used to analyse continuous variable and Wilcoxon regression for paired sample. Mc Nemar's test was used for comparison of paired nominal data and Chi-square test when data missed.
Results
The comparison of the data before and after transition is detailed in Table 1. Thirty eight patients (11 males) were included and made the transition at a median age of 20.1 years (range: 18.0-26.8). All patients were HbSS. The median age at diagnosis was 0.8 year (range: 0-7.95). The median duration of the follow-up before the transition was 15.95 years (range: 3.3 - 25.2) and after transition was 4.7 years (range: 2.2-5.8 years), accounting for 552.15 and 159.61 patient-years (PY) of follow-up respectively. Two patients died, 5.2 years and 0.6 year after the transition respectively. The death rate after transition was of 1.25/100 PY. Four women have delivered after a median gestation of 37.1 weeks (range: 35.9-38.7 weeks). The median new-born weight was 2.9 kg (range: 2.4-3.4 kg).
The rate of disease modifying therapies remains stable after the transition. 33 patients were treated with hydroxyurea before transition compared to 35 after transition. Four patients were on chronic transfusion program before and 6 after transition. Hematological data were not statistically different at time of transition when compared to last follow-up, suggesting stable compliance to therapy but creatinine level increased significantly.
VOC and ACS rate did not increased after transition as well as hospitalisation rate and days of hospitalisation.
Tricuspid regurgitation velocity (TRV) increased significantly over the time but no patient developed pulmonary hypertension. The 6-minutes walk distance decreased significantly. Systolic and diastolic blood pressure increased significantly between the time of transition and the last follow-up.
Regarding the educational status (8 data missing), 21 (70%) patients were able to reach graduate school and only 4 were not able to finish high school.
Conclusion
Our data provide useful information on the outcome during the years after transition. No increase in hospitalizations, VOC or ACS was observed. This is very different from the data provided by Blinder et al. One of the reason could be that comparing to the US situation, the Belgian Health Care System provide access and quality of healthcare even in underprivileged population. The prescription rate of HU remained unchanged and the compliance to treatment evaluated by hematological parameters remained stable. Nevertheless, changes in cardio-vascular parameters and creatinine levels suggest that despite the well-standardized follow-up for young adult patient with sickle cell disease, progressive organ damage leading to renal and cardio-vascular disease might not be prevented. However, compared to the literature, we have found less high level of TRV (9.7% vs. 24-45%), no patient with pulmonary hypertension (compared to 6-10%). In addition, our patients seems to have a better 6-minutes walk distance even in the childhood cohort (paediatrics data : 562m vs. 491m in Waltz study; adults data : 490m vs. 398m). Additional data from a larger number of patients as well as a longer period of follow-up are required to confirm the efficacy of our transition system.

Disclosures
No relevant conflicts of interest to declare.