Design, rationale, and baseline patient characteristics for the Sickle Cell Disease and CardiovAscular Risk-Red cell Exchange (SCD-CARRE) trial.
BACKGROUND: Despite wide utilization of automated red blood cell exchange (RBCX) transfusion in adult patients with sickle cell disease (SCD), no consensus or quality efficacy data exist on its use. The Sickle Cell Disease and CardiovAscular Risk- Red cell Exchange (SCD-CARRE) trial tests the hypothesis that an automated chronic RBCX transfusion strategy reduces acute health care encounters and death while improving quality of life and end-organ function (cardiac, pulmonary and renal) in participants with SCD that are at high risk of death. METHODS: Adult patients with SCD with elevated tricuspid regurgitant jet velocity (TRV) and/or chronic kidney disease were considered to be at high risk of death and were randomly assigned to RBCX plus standard of care vs standard of care alone. Participants assigned to RBCX received 12 months of exchange transfusions to maintain target pretransfusion hemoglobin S% < 30%, post-transfusion hemoglobin S% < 20%, and post-transfusion hemoglobin concentration ≥10 g/dL. All study participants were managed according to NHLBI/ASH/ATS Expert Panel guidelines. The primary endpoint was the number of SCD acute health care encounters or death over 13 months. Secondary endpoints included measures of cardiovascular and renal function, exercise capacity, patient reported outcomes (all collected at baseline, and months 4, 8, and 12), and transfusion-related adverse events (collected monthly). RESULTS: Between 2020 and 2025, the SCD-CARRE trial randomized 173 participants at 23 sites across 3 countries. Enrolled participants had mean (SD) age of 45.8 (11.8) years and 54% were female. At baseline, participants had average TRV of 2.8 (0.5) m/s such that 45.9% had a TRV between 2.5 to 2.9 m/sec and 28.1% had a TRV ≥ 3.0 m/sec. The median (Q1, Q3) eGFR in this cohort was 60 (36, 110) mL/min/1.73 m2. The median (Q1, Q3) 6-minute walk test distance was 375 meters (309, 439), the median daily steps were 3,728 (2,187, 5,821), and participants experienced a median (Q1, Q3) of 2 (1, 5) pain episodes in the year prior to randomization. The trial results are pending. CONCLUSIONS: The SCD-CARRE trial successfully enrolled a cohort of n = 173 adults with SCD. This study highlights a rationale to evaluate the effect of automated chronic RBCX transfusion strategy plus standard of care as compared to standard of care alone in SCD patients at high risk of death with a focus on patient centered outcomes, preservation of cardiovascular function, end-organ complications and death. TRIAL REGISTRATION: ClinicalTrials.gov, Identifier: NCT04084080, https://clinicaltrials.gov/study/NCT04084080.