Article

Neuropsychological speed tests and blood phenylalanine levels in patients with phenylketonuria: a meta-analysis.

Centre for Paediatric and Adolescent Medicine, University of Heidelberg, Im Neuenheimer Feld 430, D-69120 Heidelberg, Germany.
Neuroscience & Biobehavioral Reviews (impact factor: 8.65). 12/2008; 33(3):414-21. DOI:10.1016/j.neubiorev.2008.11.001
Source: PubMed

ABSTRACT Although pathogenesis of phenylketonuria is not completely understood, a low phenylalanine diet is effective to prevent severe neurological impairment, mental retardation and behavioural difficulties. Treatment recommendations heavily rely on neuropsychological research; however, single study results are ambiguous, what is reflected in substantial variation of US, British, German, Dutch and French recommendations for blood phenylalanine concentrations for adolescents and adults. We conducted a meta-analysis estimating the influence of age, phenylalanine level, and type of neuropsychological test on effect sizes (standardized differences between controls and patients) of computer-based speed measurements in phenylketonuric patients. The effect of blood phenylalanine level on effect size was more pronounced in children and adolescents than in adults, with choice reaction time being particularly sensitive for phenylalanine concentrations. Results corroborate all recommendations for children. With the exception of the US and Dutch recommendations, all recommendations for adolescents seem to be too liberal. The same effect size is predicted for adult phenylalanine concentrations between 750 and 1500mumol/L not suggesting a preference for any of the published treatment recommendations for adulthood.

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Keywords

adult phenylalanine concentrations
 
behavioural difficulties
 
blood phenylalanine concentrations
 
blood phenylalanine level
 
computer-based speed measurements
 
Dutch recommendations
 
effect size
 
effect sizes
 
French recommendations
 
low phenylalanine diet
 
mental retardation
 
neuropsychological research
 
neuropsychological test
 
phenylalanine concentrations
 
phenylalanine level
 
published treatment recommendations
 
severe neurological impairment
 
single study results
 
standardized differences
 
Treatment recommendations
 

Julia Albrecht