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Intellectual development of the patients of the German Collaborative Study of children treated for phenylketonuria

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Abstract

In a multicentric and interdisciplinary approach the German Collaborative Study of Children Treated for Phenylketonuria (PKU) investigates prospectively the effects of early started strict dietary treatment on the growth and development of 140 patients. The present paper focuses on longitudinal intelligence data from 4, 5 and 9 years of age of 89 patients in relation to the quality of dietary control in comparison to 200 healthy children tested by the same protocol. Cluster analysis of phenylalanine (Phe) levels distinguished a cluster of good dietary control with Phe levels according to the recommendation of maintaining Phe levels below 360 µmol/1, a cluster of poor dietary control with Phe levels greater than 600 µmol/1 after the age of 3 years, and a cluster of intermediate control. Intelligence quotients (IQ) and Phe clusters were inversely related with non-significant differences between the clusters good and intermediate. On average, all three clusters scored significantly lower than healthy age peers. Mean IQ scores decreased for patients as well as for healthy children due to different tests used at different measurement occasions. Patients with poor dietary control showed a steeper decrease between 4 and 5 years than patients with better dietary control. Between 5 and 9 years IQ differences between patients and healthy children remained stable. Verbal IQs were higher than performance IQs for patients as well as for healthy children. It is concluded that after early and strict treatment during the pre-school years Phe levels, in the range observed, do not influence IQ development until the age of 9 years. IQ subscale pattern indicate that PKU results in a generalized reduction of IQ instead of disturbing specific abilities. It remains to be investigated whether higher Phe levels are also innocuous and/or may result in late effects.

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Abbreviations

CMMS :

Columbia Mental Maturity Scale

IQ :

intelligence quotient

Phe :

phenylalanine

PKU :

phenylketonuria

WJSC-R :

Wechsler Intelligence Scale for Children — Revised

WPPSI :

Wechsler Preschool and Primary Scale of Intelligence

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Authors and Affiliations

  1. The German Collaborative Study of Phenylketonuria, Department of General Pediatrics, University of Heidelberg, Im Neuenheimer Feld 150, D-69120, Heidelberg, Germany

    P. Burgard, E. Schmidt, A. Rupp & H. J. Bremer

  2. Department of Psychology, University of W└zburg, Wittelsbacherplatz 1, D-97074, Würzburg, Germany

    W. Schneider

Authors
  1. P. Burgard
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  2. E. Schmidt
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  3. A. Rupp
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  4. W. Schneider
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  5. H. J. Bremer
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Burgard, P., Schmidt, E., Rupp, A. et al. Intellectual development of the patients of the German Collaborative Study of children treated for phenylketonuria. Eur J Pediatr 155 (Suppl 1), S33–S38 (1996). https://doi.org/10.1007/PL00014245

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