Algorithm for Apherisis Monitoring and Prescription Assistance in Sickle Cell Patients (ALGODREP)

Overview

The main objective of this study is to prove the superiority of a procedure which calculates the volume of RBCs to transfuse and the time between apheresis based on this algorithm, compared to the current procedure. The primary endpoint would be the number of patients with individually achieved objectives in terms of % HbS before each apheresis (which reflects the effectiveness of the previous apheresis) over a period of 12 months. The secondary objectives would be to compare the volume differences of transfused RBCs in both groups over a period of 12 months, the occurrence of clinical events and the satisfaction of patients and physicians. The investigators hope that this study would improve the efficiency and the performance of apheresis in sickle cell patients. The investigators also hope to facilitate the organization of procedures with the flexibility that would allow the use of this algorithm.

Sickle cell disease (SCD) is the most common genetic disease leading to abnormal hemoglobin (HbS). Chronic complications can be severe and affect multiple organs. Among them, cerebrovascular disease is one of the most serious leading to a high risk of stroke. These complications often require blood exchange transfusions (BET) in order to replace red blood cells (RBC) containing HbS (from patients) by GR containing HbA (blood donors), and thereby stop the harmful pathophysiological cascade. The indications of long-term apheresis are mostly, but not exclusively, represented by cerebral vasculopathy (85% in our center), and chronic organ damages. Long-term BET in cerebral vasculopathy may considerably reduce the risk of stroke while stopping them leads to a recurrence of this risk, hence there is a need to do them regularly (on average every 4 to 6 weeks) with an objective of HbS ≤ 30%. This objective may be less stringent in the case of other indications. Two methods are used: a manual method which is feasible anywhere and the apheresis which is preferred because of its better efficacy in achieving the targets of HbS percentage. It also limits transfusion hemochromatosis. The volume required for BET by apheresis as well as the optimal period between apheresis sessions are empirically determined. In our practice, the investigators noticed that this method did not allow to steadily obtaining the %HbS objective and the interval between apheresis was variable, in part conditioned by the availability of machines. This implies a real risk of occurrence of recurrent stroke in patients with cerebral vascular disease and may cause a lack of flexibility in the timing of appointments. Thereby the principal investigator and the biostatistician created an algorithm to compute the volume of blood to be transfused and the interval between apheresis which are necessary to maintain an individual objective of HbS percentage. This algorithm has been obtained by statistical analysis of apheresis performed at Henri Mondor Hospital over a period of 3 years.