In select patients with sickle cell disease (SCD), relaxing the preprocedural hemoglobin S target for red blood cell (RBC) exchange from lower than 30% to lower than 50% 3 years following a stroke might be an effective, safe option for stroke prevention.

The findings were published in a retrospective chart review analysis in the Journal of Clinical Apheresis.

Among individuals with SCD, stroke is a leading cause of morbidity and mortality, with the incidence reported to be highest during childhood and adolescence. Throughout the lifetime of a patient with SCD, the risk for stroke continues to be higher than that in the general population.

The preferred management strategy for primary and secondary stroke prevention among patients with SCD is RBC exchange. It is known that chronic RBC exchange has the potential to lower net iron accumulation compared with simple transfusion, thus helping to prevent complications related to iron overload.

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Based on results from the Stroke Prevention in Sickle Cell Anemia clinical trial and the 2020 American Society of Hemoglobin guidelines, an indefinite hemoglobin S target of lower than 30% for secondary stroke prevention is widely recognized. Use of this tactic, however, requires more frequent red RBC and more RBC units. In patients with SCD who have a low risk for stroke, the University of Texas (UT) Southwestern Medical Center in Dallas has developed a chronic RBC exchange protocol that elevates the hemoglobin S target to lower than 50%.

The researchers sought to review the medical records of patients with SCD who were receiving chronic RBC exchange with a target hemoglobin S of lower than 50% over the past 10 years in an effort to evaluate the safety of maintaining higher hemoglobin S targets in patients with SCD and a low risk for cerebrovascular accident.

Among 49 individuals with SCD enrolled in the UT Southwestern chronic RBC exchange program for secondary stroke prevention, 33 patients underwent procedures with a higher hemoglobin S target (ie, <50%)—18 women and 15 men. Participants’ ages ranged between 23 and 51 years at the end of data collection (July 2021). The mean time since patients had experienced their most recent stroke was 20.5±9.1 years.

The average enrollment period from the initial procedure to the last procedure (by July 2021) was 90.0±43.1 months. Among the 33 participants, 2 were not included in the chronic RBC exchange program—1 of whom experienced a thromboembolic event and the other in whom cerebral vasculopathy was observed on imaging. The 31 individuals who were included in the study were maintained on chronic RBC exchange at 4- to 8-week scheduled intervals with a hemoglobin S target of less than 50%.

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The average prehemoglobin S was 27.11% in the goal lower-than-30% arm and 35.46% in the goal lower-than-50% arm—a difference that was statistically significant (P =.030). Overall, 7 individuals experienced conversion between the hemoglobin S targets of lower than 50% and <30%. In 4 of them, significant reductions were seen in the frequency of RBC exchange and use of blood volume.

“The findings suggest that liberalizing the hemoglobin S target could confer clinical flexibility without increasing the risk [for] cerebrovascular accident in a selective population,” the researchers noted. “Further studies to fully evaluate the potential benefits of this approach are indicated,” they concluded.


Choi J, Markantonis JE, De Simone N, Nero A, Kim J, Sarode R. Hemoglobin S target of <50% as compared to 30% in chronic red cell exchange for secondary stroke prevention in sickle cell disease. J Clin Apher. Published online August 1, 2023. doi:10.1002/jca.22078