University of Texas Southwestern Southlake, Texas, United States
Background/Case Studies: Red blood cells (RBCs) accumulate biochemical and biomechanical changes during storage, which can reduce their viability after transfusion. To maximize the benefits of chronic RBC exchange in sickle cell disease patients, fresh RBC units have been advocated. However, no standard policy exists regarding the freshness of RBCs for exchange, and the impact of fresh RBC units on chronically transfused sickle cell disease patients remains unclear. This study sought to determine the effects of RBC storage duration on subsequent survival following RBC exchange.
Study
Design/Methods: This retrospective cohort study was conducted at the University of Texas Southwestern Medical Center Clements University Hospital and Parkland Memorial Hospital in Dallas, Texas. The study was approved by the University of Texas Southwestern Medical Center institutional review board. Between January 2024 and January 2025, the number and age of RBC units at the time of exchange were collected when a waiver of the RBC freshness requirement was requested. Laboratory findings (% HbA, % HbS, hematocrit) before and after RBC exchange and the procedure date were collected by retrospective chart review. Eight patients received more than nine units of freshness-waived RBCs (average age 15.8±2.0 days). RBC life spans were calculated from the procedure performed with freshness-waived RBC units and from other procedures performed with less than 7 day old RBC units within 1 year, using the previously described method [1]. Statistical significance was determined by one sample t-test with p< 0.05 as the threshold. All statistical analyses were performed using GraphPad software (GraphPad, Boston, MA, USA).
Results/Findings: The calculated RBC lifespan from freshness-waived RBC units was 123.7±25.2 days vs. 133.0±24.5 days for controls (Table 1). The average Z-score calculated against control RBC exchanges was -0.465±0.457 (p-value 0.016), and the RBC lifespan ratio was 0.94±0.07 (p-value 0.024).
Conclusions: Freshness-waived RBC units exhibited statistically significant differences in calculated RBC lifespan from control units in 8 sickle cell disease patients receiving chronic RBC exchange. This result aligns with earlier research showing that prolonged storage reduced the survival of RBCs following transfusion. However, the calculated RBC lifespan of freshness-waived units (123.7±25.2 days) was longer than the typical RBC exchange interval of every 4-8 weeks, raising questions about whether strict adherence to the RBC freshness requirement can provide sufficient benefits to justify the additional burden on the RBC supply. Further study to model and assess the impact of transfusing older RBC units on the HbA RBC mass at the time of the subsequent exchange procedure using a larger number of patients appears indicated.
