Contribution to the problems of determining heterozygotes in phenylketonuria by the biochemical and electroencephalographic method.

The authors describe their experiences with the determination of heterozygotes in phenylketonuria. They employed: 1. a biochemical method based on a peroral phenylalanine loading test, and 2. an electroencephalographic method using Pentazol stimulation to demonstrate characteristic changes in the EEG curve of individuals with phenylketonuria. The biochemical methods normally available in clinical practice do not allow absolutely exact differentiation of heterozygotes from unafflicted individuals. The authors' experiences show that combination of the biochemical method (loading test) with the electroencephalographic method makes differentiation more accurate.