title: Intelligence quotient in paediatric sickle cell disease: a systematic review and meta-analysis.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Developmental Neurosciences, Institute of Child Health, University College London, London, UK.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Kawadler
authors.affiliation: Developmental Neurosciences, Institute of Child Health, University College London, London, UK.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Clayden
authors.affiliation: Developmental Neurosciences, Institute of Child Health, University College London, London, UK.
authors.forename: Chris A
authors.initials: CA
authors.lastname: Clark
authors.affiliation: Developmental Neurosciences, Institute of Child Health, University College London, London, UK.|Clinical and Experimental Sciences, University of Southampton, Southampton, UK.
authors.forename: Fenella J
authors.initials: FJ
authors.lastname: Kirkham
mesh_terms: D000755:Anemia, Sickle Cell / Q000150:complications* / Q000000981:diagnostic imaging; D002658:Developmental Disabilities / Q000000981:diagnostic imaging / Q000209:etiology; D006801:Humans; D008607:Intellectual Disability / Q000000981:diagnostic imaging / Q000209:etiology*; D007361:Intelligence Tests; D008279:Magnetic Resonance Imaging; D039781:PubMed / Q000706:statistics & numerical data