Significant decrease in ECV from baseline to 1- and 12-month post-HCT. The gray points connected by gray lines are the individual values of the ECV at the baseline, 1-month, and 12-month time point for each participant. The genotype is denoted by solid lines with circles (HbSS) or dashed lines with triangles (HbSC). The red dots and red line represent the mean of these ECV values, and the red shaded area connects the 95% confidence intervals for the mean at baseline, 1 month after HCT, and 12 months after HCT. The gray rectangular area next to the vertical axis represents the normal range for ECV levels. The P value shown (.005) is from a likelihood ratio test from the linear mixed effects model to assess whether mean ECV differed from baseline at 1 and/or 12 months. The time point–specific paired t test P values are .061 and .002 for the 1- and 12-month comparisons with baseline, respectively.