INTELLECTUAL AND SCHOOL PERFORMANCE IN ADOLESCENTS WITH PHENYLKETONURIA ACCORDING TO THEIR DIETARY COMPLIANCE - THE CZECH-SLOVAK COLLABORATIVE STUDY

The intellectual development and school performance of 81 adolescents with hyperphenylalaninaemia type I between the ages 15 and 19 years we re evaluated in a retrospective study. All adolescents were born betwe en 1975-1979. In spite of the continuous changes and improvement of di etary treatment, there were no differences in the dietary approach in all phenylketonuria centres involved. A significant negative correlati on between IQ of adolescents with phenylketonuria and the onset of die tary treatment was observed (r = -0.37, P < 0.01). The best school per formance was found in the group of adolescents with dietary therapy wh ich was introduced in the first weeks of life. There was no correlatio n between IQ of the adolescents and their phenylalanine level in the n eonatal period. There was a significant negative correlation between I Q of adolescents and the average level of blood phenylalanine in the f irst 5 years of life (r = -0.32, P < 0.01), but this correlation was l ess significant later on and was not present after the age of 14 years . Dietary compliance was much more difficult to achieve in adolescence than in childhood.