Pooled analysis of the 7 studies documenting TCD measurement before and after hydroxyurea therapy from DeBaun and Kirkham.¹³  The pooled analysis based on the random effect model demonstrating the average drop in TCD measurement after starting hydroxyurea therapy of 25 cm per second. The table also includes the observation that the decrease in TCD measurements can be seen as early as 3 months after starting hydroxyurea therapy, with a sustained impact of hydroxyurea therapy on decreasing TCD measurements for at least 36 months. The black diamond represents the results of random effect model. The edges of the diamond represent the 95% CI of the meta-analyses for the random effect model.^13,22-25  Figure reproduced from DeBaun and Kirkham.¹³