1 The deBelle Laboratory for Biochemical Genetics, McGill University-Montreal Children's Hospital Research Institute, Montreal, P.Q.
THE recent interest in metabolic screening in the newborn period stems from the belief that early detection of certain hereditary metabolic diseases provides the best opportunity to initiate treatment. It has been implied generally that identification of an aberrant biochemical phenotype is synonymous with disease; treatment ought, therefore, to be initiated to restore the normal phenotype in order to prevent harm to the patient. A practical application of this philosophy emerged in the case of phenylketonuria; a nation-wide alert to prevent mental retardation provided fertile ground for "phenylketonuria" screening programs to take root and appear abruptly in the mainstream of medical care. Many state legislatures were convinced that eradication of any cause of mental retardation was an important venture; thus, enabling or compulsory legislation was passed to achieve this end. How to interpret the "positive screening test" and how to divine its true significance has, therefore, become a problem which could face any pediatrician at any time in North America today.
A recent editorial in Pediatrics commenting on neonatal screening programs noted that they may bring both good and harm. An accompanying article described the vicissitudes which beset several investigators of neonatal tyrosinemia. Early impressions suggested that infants would benefit from treatment of their tyrosinemia; however, the need for treatment in most infants with tyrosinemia was not substantiated after more detailed investigations had been performed. It is easy to see how harm might have been done in terms of quite unnecessary treatment for neonatal tyrosinemia, although at one point it seemed that it might be good to screen all infants for neonatal tyrosinemia.