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Wechsler subscale IQ and subtest profile in early treated phenylketonuria

P V Griffiths1, C Demellweek, N Fay

  • 1Department of Psychology, University of Stirling and Royal Hospital for Sick Children, Glasgow G3 8SJ, UK. pvg1@stir.ac.uk

Archives of Disease in Childhood
|February 24, 2000
PubMed

Insights

Early phenylketonuria (PKU) treatment improves verbal IQ but may not normalize spatial skills. Good phenylalanine control in infancy is key for cognitive development in children with PKU.

Area of Science:

  • Neuroscience
  • Genetics
  • Developmental Psychology

Background:

  • Phenylketonuria (PKU) is a genetic disorder requiring early dietary intervention.
  • Mildly depressed IQ is frequently observed in treated PKU patients.
  • Understanding cognitive profiles in treated PKU is crucial for optimizing care.

Purpose of the Study:

  • To determine if early and continuously treated PKU exhibits a specific intellectual ability profile.
  • To investigate the relationship between IQ components and socioeconomic/treatment factors.

Main Methods:

  • Retrospective analysis of Wechsler intelligence scale for children (WISC) scores at age 8 in 57 early-treated PKU children.
  • Examination of WISC subscale/subtest scores and historical phenylalanine blood concentrations.

Main Results:

  • Mean full-scale IQ was 91.11, significantly below population norms.
  • A discrepancy between verbal IQ (94.65) and performance IQ (89.42) suggested spatial deficits.
  • Phenylalanine control at age 2 predicted overall IQ; levels <360 micromol/litre correlated with higher IQ.

Conclusions:

  • Early PKU treatment doesn't always normalize overall IQ.
  • Infant phenylalanine control (<360 micromol/litre) may normalize verbal IQ, but spatial intelligence may remain impaired.
  • Cognitive discrepancies are not explained by social status or treatment variables alone.
Abstract

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