title: To cut a short test even shorter: reliability and validity of a brief assessment of intellectual ability in schizophrenia--a control-case family study.
abstract: BACKGROUND
  The potential inclusion of cognitive assessments in the DSM-V and large time-consuming assessments drive a need for short tests of cognitive impairments. We examined the reliability and validity of a brief, 15-minute, version of the Wechsler Adult Intelligence Scale-III (WAIS-III).
  
  
  METHODS
  The sample consisted of patients diagnosed with schizophrenia (n=75), their siblings without schizophrenia (n=74) and unrelated healthy controls (n=84). A short WAIS-III consists of the Digit Symbol Coding subtest, and every second (or third) item of Block Design, Information, and Arithmetic. Psychometric analyses were implemented using item-response theory (IRT) to determine the best minimal item short version, while maintaining the sensitivity and reliability of the IQ score.
  
  
  RESULTS
  The proposed 15-minute WAIS-III gave reliable estimates of the Full Scale IQ (FSIQ) in all three groups in the sample. The 15-minute (select-item) version yielded an overall R of.95 (R(2)=.92) and IRT yielded an R of .96 (R(2)=.92). All four subtests performed well in differentiating patients, relatives, and healthy controls. Multivariate analysis showed a significant difference in FSIQ-estimate between patients, relatives, and healthy controls, F(2, 202) = 19.00, p < .0001. Regression modelling showed that the three versions of the WAIS had similar associations with functional outcome after a 3-year follow-up.
  
  
  CONCLUSIONS
  Our proposed 15-minute version of the WAIS may serve as a useful screening device for general intellectual ability in research or clinical settings, and is recommended when a quick and accurate IQ estimate is desired.
authors.affiliation: a Department of Early Psychosis , Academic Medical Center , Amsterdam , The Netherlands.
authors.forename: Eva
authors.initials: E
authors.lastname: Velthorst
authors.forename: Stephen Z
authors.initials: SZ
authors.lastname: Levine
authors.forename: Cecile
authors.initials: C
authors.lastname: Henquet
authors.forename: Lieuwe
authors.initials: L
authors.lastname: de Haan
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
authors.forename: Inez
authors.initials: I
authors.lastname: Myin-Germeys
authors.forename: Abraham
authors.initials: A
authors.lastname: Reichenberg
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000175:diagnosis* / Q000523:psychology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007360:Intelligence; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011594:Psychometrics / Q000592:standards; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D014888:Wechsler Scales / Q000592:standards*; D055815:Young Adult