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

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.