title: Classification of intellectual disability using the Wechsler Intelligence Scale for Children: Full Scale IQ or General Abilities Index?
abstract: OBJECTIVE
  We examined the implications of using the Full Scale IQ (FSIQ) versus the General Abilities Index (GAI) for determination of intellectual disability using the Wechsler Intelligence Scales for Children, fourth edition (WISC-IV).
  
  
  METHODS
  Children referred for neuropsychological assessment (543 males, 290 females; mean age 10y 5mo, SD 2y 9mo, range 6-16y) were administered the WISC-IV and the Adaptive Behavior Assessment System, second edition (ABAS-II).
  
  
  RESULTS
  GAI and FSIQ were highly correlated; however, fewer children were identified as having intellectual disability using GAI (n=159) than when using FSIQ (n=196). Although the 44 children classified as having intellectual disability based upon FSIQ (but not GAI) had significantly higher adaptive functioning scores than those meeting intellectual disability criteria based upon both FSIQ and GAI, mean adaptive scores still fell within the impaired range. FSIQ and GAI were comparable in predicting impairments in adaptive functioning.
  
  
  CONCLUSIONS
  Using GAI rather than FSIQ in intellectual disability diagnostic decision-making resulted in fewer individuals being diagnosed with intellectual disability; however, the mean GAI of the disqualified individuals was at the upper end of criteria for intellectual impairment (standard score 75), and these individuals remained adaptively impaired. As GAI and FSIQ were similarly predictive of overall adaptive functioning, the use of GAI for intellectual disability diagnostic decision-making may be of limited value.
authors.affiliation: Department of Neuropsychology, Kennedy Krieger Institute, Baltimore, MD 21231 USA. koriakin@kennedykrieger.org
authors.forename: Taylor A
authors.initials: TA
authors.lastname: Koriakin
authors.forename: Mark D
authors.initials: MD
authors.lastname: McCurdy
authors.forename: Aimilia
authors.initials: A
authors.lastname: Papazoglou
authors.forename: Alison E
authors.initials: AE
authors.lastname: Pritchard
authors.forename: T Andrew
authors.initials: TA
authors.lastname: Zabel
authors.forename: E Mark
authors.initials: EM
authors.lastname: Mahone
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Jacobson
mesh_terms: D000223:Adaptation, Psychological / Q000145:classification; D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000145:classification* / Q000175:diagnosis* / Q000523:psychology; D007360:Intelligence; D008297:Male; D009483:Neuropsychological Tests; D012680:Sensitivity and Specificity; D014888:Wechsler Scales