IMPROVED IDENTIFICATION OF HETEROZYGOTES FOR PHENYLKETONURIA USING BLOOD NEOPTERIN AND BIOPTERIN

A novel approach that combines information provided by the metabolism of pteridines and that of phenylalanine has been applied to the detect ion of heterozygotes for phenylketonuria. Phenylalanine, tyrosine, bio pterin and neopterin have been measured in serum from normal controls and heterozygotes for classical phenylketonuria, before and after a ph enylalanine oral load. Significant differences in neopterin and biopte rin mean values in fasting serum and in the mean increase of biopterin induced by the phenylalanine load were found between groups. Inclusio n of pteridine data in the discriminant analysis significantly improve d the resolution of the classical phenylalanine loading test for the d etection of heterozygotes for phenylketonuria.