Transcranial Doppler screening in Nigerian children with sickle cell disease: A 10-year longitudinal study on the SPPIBA cohort

Background: Primary stroke prevention programmes for children with sickle cell disease (SCD) have been shown to be feasible interventions in resource-poor countries. Different hydroxyurea (HU) regimens have been utilised in ameliorating the severity of SCD. Objective: To determine the long-term outcomes of the stroke prevention programme for children with SCD in Ibadan (SPPIBA), Nigeria. Methods: A longitudinal study of 396 children with haemoglobin SS disease who had been on the stroke prevention programme for a minimum period of 5 years. All enrollees had nonimaging TCD performed at baseline and thereafter 3-monthly or annually. Children with TCD velocities >= 170 cm/s were treated with HU by dose-escalation regimen. Results: The mean age at first TCD examination was 102 +/- 46.7 months and the period of follow-up ranged from 5 to 10 years (mean = 7.2 +/- 1.7). Time to significant decline in TCD velocities ranged from 5 to 35 months, (median = 10.0 months). The minimum dose of HU required to achieve significant decline in TCD velocities ranged from 15 to 31 mg/kg/day, mean 23.7 (+/- 3.9). HU dose escalation beyond 20 mg/kg/day was required to attain significant reductions in the time-averaged mean of maximal velocities (TAMMV) in 69.1% of the cases. Two stroke events occurred giving a stroke incidence of 0.08 per 100 patient-years. Conclusion: The majority of Nigerian children with SCD and elevated TCD velocities achieved significant decline in TAMMV within the first year of HU therapy but on higher doses of HU. It might be important to individualise HU doses for optimal outcomes in primary stroke prevention.