Intelligence quotient in paediatric sickle cell disease: a systematic review and meta‐analysis

Aim Sickle cell disease (SCD) is the commonest cause of childhood stroke worldwide. Magnetic resonance imaging (MRI) is routinely used to detect additional silent cerebral infarction (SCI), as IQ is lower in SCI as well as stroke. This review assesses the effect of infarction on IQ, and specifically whether, compared to healthy controls, IQ differences are seen in children with SCI with no apparent MRI abnormality. Method A systematic review was conducted to include articles with an SCD paediatric population, MRI information, and Wechsler IQ. A meta‐analysis of 19 articles was performed to compare IQ in three groups: stroke vs SCI; SCI vs no SCI; and no SCI vs healthy controls. Results Mean differences in IQ between all three groups were significant: stroke patients had lower IQ than patients with SCI by 10 points (six studies); patients with SCI had lower IQ than no patients with SCI by 6 points (17 studies); and no patients with SCI had lower IQ than healthy controls by 7 points (seven studies). Interpretation Children with SCD and no apparent MRI abnormality have significantly lower IQ than healthy controls. In this chronic condition, other biological, socioeconomic, and environmental factors must play a significant role in cognition. What this paper adds Systematic review of all IQ studies using Wechsler scales in patients with silent cerebral infarction (SCI) with magnetic resonance imaging (MRI). Meta‐analysis shows hierarchy for IQ by MRI status. Critical appraisal of SCI lesion size quantification studies. Critical appraisal of appropriate control comparison group. Discussion of non‐radiological biological, socioeconomic, or environmental factors associated with lowered IQ.