[Heterozygote detection in phenylketonuria by means of an oral load of phenylalanine].

The testing of heterozygosity for PKU by mean of an oral load of phenylalanine is a widely used method. In this paper, the need of a genetic counselling for two adults, with family story of PKU, lead us to reinvestigate criteria of heterozygote recognition. With all variables of the phenylalanine tolerance test, overlapping and mis classification occured. Probability density functions plotting, as proposed by GOLD, illustrated well the genetic risk of a patient. However, in practice, the heterozygote likelihood ratio determination seemed to be the best way to avoid possibly erroneous categoric statement by correcting the ratio for the a priori probability of heterozygosity.