Table 1.
Showing baseline and study laboratory and anthropometric characteristics of subjects.
Values are medians with 10th and 90th percentile in bracket, except for fetal hemoglobin percent which is expressed in means ± SD. Except for percent fetal hemoglobin (standard t-test), all comparisons were done using a Mann-Whitney test (non-parametric t-test). At baseline, there was no significant difference between subjects on all characteristic except hemoglobin level which was significantly higher among those randomized to receive standard care (p = 0.021) those who were to receive transfusion. At study exit, the group that got transfused had significantly higher hemoglobin level (p = 0.006) and lower TCD velocity (p = 0.002) than the group who did not receive transfusion. Note that those randomized to standard care still got some blood transfusion in the course of the study, but analysis was based on intent to treat. At the one year post-trial time point, TCD velocity (p = 0.034) and for an unknown reason, BMI (p = 0.031) were significantly lower among those who were originally randomized to receive transfusion in the STOP study compared to those randomized to SC. Tx = transfusion.
Fig 1.
Baseline and study exit values of von Willibrand Factor (vWF), thrombin antithrombin (TAT) complex, D-dimer and transcranial Doppler (TCD) velocity.
HbAA, SNTCD, SC and Tx refers to healthy African American children with normal hemoglobin, sickle cell subjects with normal TCD velocity, STOP subjects randomized to the Standard Care arm and sickle cell subjects randomized to the Transfusion arm respectively. * = p <0.05, ** = p <0.01, *** = p <0.001 and **** = p <0.0001.
Fig 2.
Percentage reduction in levels of coagulation biomarkers and TCD velocities in Standard Care vs. Transfusion subjects, comparing study exit to baseline values.
von Willibrand Factor (VWF) (A), thrombin antithrombin (TAT) complex (B), D-dimer (C) and TCD velocity (D). SC and Tx represents sickle cell subjects randomized to the Standard Care and Transfusion arms respectively. *** = p <0.001 and **** = p <0.0001.
Fig 3.
Correlation of transcranial Doppler ultrasound velocity with serum levels of biomarkers of coagulation.
Serum von Willibrand Factor (vWF) (A), thrombin antithrombin (TAT) complex (B) and D-dimer (C) levels at baseline were significantly positive except for D-dimer (3C).
Fig 4.
Plots of coagulation biomarker levels or TCD velocity against total number of PRBC transfusions received over the course of the trial.
von Willibrand Factor (vWF) (A), thrombin antithrombin (TAT) complex (B), D-dimer (C) levels and TCD velocity (D) All 3 biomarkers and TCD velocity show significant negative correlation with number of blood PRBC transfusion. Note in the figure the almost clear separation of subjects randomized to no transfusion (open diamond) and transfusion (solid circles) arms based on the number of PRBC transfusions received. Standard care arm = Open diamond. Transfusion arm = Solid circle.