A SIMPLE PHENYLALANINE METHOD FOR DETECTING PHENYLKETONURIA IN LARGE POPULATIONS OF NEWBORN INFANTS

TLDR

A new method is described for rapid and economical screening of large numbers of hospital nursery infants for elevation in blood phenylalanine associated with phenylketonuria. The method employs a simple phenylalanine assay to rapidly and economically screen newborns. In a cohort of 682 infants (mostly 4 days old), no phenylalanine levels exceeded 4 mg/100 ml, only 8 % were above 2 mg/100 ml, matching other methods and indicating a very low false‑positive rate; a level ≥6 mg/100 ml is recommended as positive and should be confirmed with a second specimen.

Abstract

A new method is described for rapid and economical screening of large numbers of hospital nursery infants for elevation in blood phenylalanine associated with phenylketonuria. Results are presented for 682 infants, 96% of whom were 4 days of age. None of the blood phenylalanine values were found to be as high as 4 mg/100 ml, and only 8% were above 2 mg/100 ml. These values appear to be in agreement with values obtained by other methods, and indicate that a very low rate of "false-positives" will be encountered during screening of the 10,000 or more infants that may be necessary to detect a case of phenylketonuria. It is recommended that any result of 6 mg/100 ml or above be considered positive, and require confirmation by phenylalanine determination of a second blood specimen.