(P-TS-77) Pitted Red Blood Cell Count Correlates with Spleen Volume in Adolescents and Adults with Sickle Cell Disease on Chronic Transfusion Therapy

Sunday, October 20, 2024

12:00 PM - 1:00 PM

Presenting Author(s)

Marianne E.M Yee, MD, MSCR (she/her/hers)

Associate Professor of Pediatrics, Hematology
Emory University and Children's Healthcare of Atlanta
Atlanta, Georgia, United States

Background/Case Studies: Chronic transfusion therapy (CTT) is an essential therapy for many patients with sickle cell disease (SCD). Considerable variation in transfusion survival and recovery is observed among different patients, impacting outcomes of sickle hemoglobin (HbS) suppression and hemolysis. Transfused donor red blood cells (RBCs) are primarily cleared by phagocytic activity in the spleen and liver. All patients with SCD are considered to have functional asplenia starting in infancy, but a range of splenic activity exists. Splenectomy may be required for patients with repeated sequestration or hypersplenism. While direct measurement of splenic phagocytic activity is impractical, pitted RBC (RPIT) indicate splenic dysfunction. Many studies have examined RPIT thresholds to categorize normal vs. abnormal spleen function, however there are no studies examining the range of high abnormal RPIT in adolescents or adults with SCD.

Study

Design/Methods: Adolescent and young adult patients with SCD receiving CTT were enrolled. Blood bank antibody histories were reviewed; alloimmunization was classified as a past history of defined alloantibody or antibody of undetermined specificity but excluded history of solely RBC autoantibody or solid phase reactivity only. Two to 3 days prior to the transfusion, spleen dimensions were measured by ultrasound, and RPIT was measured by microscopy (Cincinnati Children’s Erythrocyte Diagnostic Laboratory). Spleen volume was estimated by: 0.524 x Width x Thickness x (Maximal Length + Craniocaudal Length)/2. Statistical comparisons were done by Pearson’s correlation, Student’s t-test, or Fisher’s exact test, as appropriate.

Results/Findings: 18 subjects with HbSS or HbSβ⁰-thalassemia were enrolled: 12 pediatric (mean age 16.2 years, range 12 – 21 years) and 6 adult (mean age 29.8 years, range 25 – 33 years). Six (33%) had alloimmunization, and 5 (28%) had splenectomy with absent spleen verified by ultrasound; 1 adult patient without splenectomy had no identifiable spleen tissue. Splenectomy frequency was 50% among those with alloimmunization vs. 17% for those without alloimmunization (p=0.27). Mean spleen volume in non-splenectomized patients was 99.3 mL for pediatrics vs. 49.4 mL for adults (p=0.08). RPIT correlated significantly with age for all subjects (r=0.52, p=0.029, n=18) and for those without splenectomy (r=0.59, p=0.032, n=13). RPIT negatively correlated with spleen volume (r= -0.52, p=0.028, Figure 1). In pediatrics, there was a non-significant trend of higher RPIT in those with alloimmunization (mean RPIT 26.7% vs. 16.1%, p=0.088).

Conclusions:

RPIT, used to identify splenic dysfunction, may also be a useful indicator of spleen size and activity, impacting patients with SCD receiving transfusions.