Screening for Phenylketonuria

To the Editor: The claim by Meryash et al.¹ in the January 29 issue that “newborns who have PKU [phenylketonuria] can be identified by routine screening during the first 48 hours of life” is based on few observations, and it ignores published data.^{2 3 4} Although the diagnosis can usually be made by early screening, the likelihood of a false-negative result is greater in the first 48 hours of life than later. In 1970 and 1971, PKU clinics provided the results of serial determinations of blood phenylalanine in 47 newborn siblings of children known to be phenylketonuric; the siblings themselves were also. . .