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Am J Hematol. 2015 Dec;90(12):1099-105. doi: 10.1002/ajh.24198. Epub 2015 Nov 17.

Prevention of conversion to abnormal transcranial Doppler with hydroxyurea in sickle cell anemia: A Phase III international randomized clinical trial.

Author information

Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee.
Sickle Cell Unit, Tropical Medicine Research Institute (TMRI), University of the West Indies, Kingston, Jamaica.
Instituto De Hematologia Arthur Siqueira Cavalcanti (HEMORIO), Rio De Janeiro, Brazil.
Division of Pediatric Hematology/Oncology and Stem Cell Transplantation, Cohen Children's Medical Center of New York, New Hyde Park, New York.
Wake Forest University School of Medicine, Winston-Salem, North Carolina.
National Heart Lung and Blood Institute, Bethesda, Maryland.
Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.


Children with sickle cell anemia (SCA) and conditional transcranial Doppler (TCD) ultrasound velocities (170-199 cm/sec) may develop stroke. However, with limited available clinical data, the current standard of care for conditional TCD velocities is observation. The efficacy of hydroxyurea in preventing conversion from conditional to abnormal TCD (≥200 cm/sec), which confers a higher stroke risk, has not been studied prospectively in a randomized trial. Sparing Conversion to Abnormal TCD Elevation (SCATE #NCT01531387) was a National Heart, Lung, and Blood Institute-funded Phase III multicenter international clinical trial comparing alternative therapy (hydroxyurea) to standard care (observation) to prevent conversion from conditional to abnormal TCD velocity in children with SCA. SCATE enrolled 38 children from the United States, Jamaica, and Brazil [HbSS (36), HbSβ(0) -thalassemia (1), and HbSD (1), median age = 5.4 years (range, 2.7-9.8)]. Because of the slow patient accrual and administrative delays, SCATE was terminated early. In an intention-to-treat analysis, the cumulative incidence of abnormal conversion was 9% (95% CI = 0-35%) in the hydroxyurea arm and 47% (95% CI = 6-81%) in observation arm at 15 months (P = 0.16). In post hoc analysis according to treatment received, significantly fewer children on hydroxyurea converted to abnormal TCD velocities when compared with observation (0% vs. 50%, P = 0.02). After a mean of 10.1 months, a significant change in mean TCD velocity was observed with hydroxyurea treatment (-15.5 vs. +10.2 cm/sec, P = 0.02). No stroke events occurred in either arm. Hydroxyurea reduces TCD velocities in children with SCA and conditional velocities.

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