Effect of baseline rheology on rheological changes at MTD of HU. Horizontal dotted line denotes mean baseline values. A. Patients with HbSS and a baseline HVR 45 s^-1 below the mean showed an increase in HVR 45 s^-1 at MTD (green dots). B. Patients with HbSS and a baseline HVR 225 s^-1 below the mean showed an increase in HVR 225 s^-1 at MTD (green dots).